For the light side to only have a slim chance of winning (e.g. A Memory of Light) then the Light side has to be pretty much screwed by the end of Towers of Midnight. So far, the books haven't been heading in that direction, if you ask me. For example, while the Shadow had a lot of potential in Mesaana and Halima/Aran'gar, both of those threads ended in TGS with the Light side having major victories:

1) The White Tower is in a VASTLY BETTER situation now than it was at the beginning of TGS.

While the WT isn't at its ideal, 2) the Black Ajah have been exposed and are all on the run, except for Mesaana.

3) Halima can't show her face because the risk of someone recognizing her is too great, thus Halima has to go find a new center of power.

4) Graendal appears dead (or might not be).

5) Semirhage is dead.

6) The one weapon (the Choedan Kal) that could be used to destroy the world was destroyed by Rand. Now the Shadow will have to attempt to destroy the world the old fashioned way.

7) Padan Fain, the one true wild card, is still alive, interfering with plans for the good and the bad guys.

Elayne secured the Lion Throne and united most (almost all) of Andor.

9) The Shadow had a huge opportunity to overrun the Borderlands, but they seemed to have missed this chance. Rand seems to have neutralized that threat by sending Rodel Ituralde and hundreds of Asha'man to protect the Borderlands.

10) Nynaeve sent Lan to the Borderlands to help raise more troops. Admittedly, Shienar and Kandor are probably still left exposed, but Saldaea and probably Arafel are now protected via Lan's army, Rodel Ituralde and the Asha'man.

11) Suroth's attempted murder of Tuon was thwarted by Mat and Tuon has absolute control of the Seanchan now.

12) The Shaido, a force that could have interrupted things was destroyed.

13) Perrin rescued Faile and is amassing a huge army of fanatically devoted followers who love him maybe more than any ruler. Although it happened off-screen, we saw in TGS that Galad's forces have met up with Perrin and even though there is going to be some tension between Perrin and the Whitecloaks, Galad has got to be more help than hinderance.

14) Masema was killed.

15) Because of Perrin's truce/alliance with the Seanchan, Ghealdan is more likely now than before to be able to produce men for Perrin and thus for Tarmon Gaidon.

16) Rand still has the Aiel support, but admiteddly it is waning.

17) Verin interrupted probably just about every Black Ajah plot she possibly could. Thus, Verin's note probably tells Mat that one of the sisters in his group is Black Ajah. Verin's other notes she had to deliver probably warned others of similar things. Verin single handedly probably did more harm to the Shadow than anyone else except Rand.

I could go on and on, but I'll stop.

Basically, the end of TGS was like Star Wars: A New Hope (episode 4). The good guys appear to be winning. So now I'm waiting to see The Empire Strikes Back (episode 5), that is, see the Forsaken and bad guys start winning.

Let me list The Wildcards
1. Murandy and King Roedran
2. The Borderlander 200K men (possibly controlled by a Forsaken)
3. Padan Fain

Here are the Known bad guys
1. The Black Ajah that could travel, and therefore, the most powerful BA, escaped.
2. Mazrim Taim has run loose and probably has around 400 Asha'man on his side and thus directly in the Shadow's control.
3. Mazrim Taim has probably captured many good Aes Sedai and enslaved them via the bond to the evil men under his control.
4. Demandred is still alive.
5. Moridin.
6. Cyndane and Moghedien - we've seen very little of them and we don't know what they've been up to, but probably something evil.
7. Halima/Aran'gar is still alive.
8. Mesaana is still alive, but being hunted by Egwene.

There are two bad guy advantages that shouldn't be forgotten.
1. The Seanchan know (or soon will know) how to travel. While no Forsaken is controlling the Seanchan at the moment, the Seanchan could still do great harm to the Light's cause just because Tuon will interfere with Rand's and Egwene's plans because she is a haughty, arrogant, and childish person. She is still 100% opposed to the White Tower and 75% opposed to Rand.

2. The Waygate on the Shadow coast never got closed. Who knows how many tens of thousands (maybe hundreds of thousands) of trollocs are about to invade Tarabon, Amadicia, and Altara.

Now, I mentioned above that in order for there only to be a Memory of Light for the good guys by the end of ToM that a lot of bad things have to happen. So here is what I envision.

Predictions
1. Mazrim Taim has already sent or will send 100 or so of his loyal Asha'man to join and command the hundreds of thousands of trollocs along the Shadow Coast. They wait for the Seanchan to launch major attacks east into Illian and north into Andor. Once the Seanchan are distracted, the Shadow Coast force of trollocs/Asha'man attacks, devastating all of Tarabon, Amador, and Altara. The Seanchan are caught by surprise and Tarabon, Amador, and Altara are left completely unable to contribute anything to help the Light.

2. Even though Semirhage is dead, her plans will survive her, doing much harm to the Light. Semirhage set Tuon on a collission course with Andor and Illian. Therefore, Tuon, bolstered by her newly acquired ability to travel (although not in large numbers because they cannot form circles) launches major attacks into Andor and Illian. The Seanchan engage Rand's Aiel in Illian, it is a draw and both sides lose major numbers. Similarly, the Seanchan launch a northern front attack into Andor or Ghealdan, probably conquering Ghealdan (Perrin can't stop them) and at the very least disrupting western Andor.

3. The Seanchan spend weeks trying to settle Arad Doman down, but have to abandon that country to divert forces back to the south to counter the invasion of the Shadow coast trollocs. The Seanchan force in Arad Doman finally stops the Shadow Coast trollocs advance somewhere in northern Tarabon or on Almoth Plain, but by that time, the Seanchan have not enough men to hold Arad Doman, or even Almoth Plain. Both those areas are left in chaos, and the Seanchan are trying to pick up the remnants of Tarabon.

4. Mazrim Taim sends a hundred or so Asha'man and some/all of Egwene's captured Aes Sedai to fight along side the Trollocs in the Borderlands. Rand and Rodel Ituralde only thought they could hold back the trollocs with the addition of Rand's Asha'man. Rand and Rodel Ituralde had not figured on Mazrim Taim's Asha'man contributing to the Shadow's force and thus Rand's Asha'man are neutralized by Mazrim Taim's Asha'man. Therefore, it comes down to who has the larger human force and we already know the Shadow can easily overrun the Borderlands without Rand's Asha'man. Consequently, the Shadow overruns Saldaea and Kandor.

5. Demandred, or whichever Forsaken is controlling the Murandy force, causes the Murandians to get into a war with the Borderlanders. The borderlanders win, and Murandy is destroyed.

6. The Borderlander army then engages the Seanchan as they move north from the Mulvaine Gap towards Andor. The Borderlanders are defeated and have to retreat, but the Seanchan end up retreating too after they get orders to come back to Altara because there are hundreds of thousands of trollocs on the loose supported by male channelers and captured AS ransacking Altara.

7. Rand really angers the Aiel this time and several clans decide not to follow him anymore and head back east to the three fold land (maybe 3-5 clans do this).

8. The trollocs destroy Shienar, Kandor, and Arafel. Lan's army doesn't arrive in time or it is stopped by the trollocs that overan Saldaea and Rodel Ituralde. Lan's hope of fighting for his homeland never comes to fruition once he realizes there is no homeland left to fight for (its already been destroyed) and it is all he can do to stay alive in Saldaea.

9. The Sea Folk decide not to honor a request of Rand's at a key moment because he has been ignoring his agreement to keep a sea folk emissary with him at all times. This causes Rand to lose a major battle and/or to declare his alliance/agreement with the Sea Folk ended. The Sea Folk depart in anger, and there is no hope they will help the light at Tarmon Gai'don.

10. Graendal turns out not to be dead and invades Tear with an army of Sharans and Sharan channelers. Rand loses Tear.

11. A couple of good guys die (please let it be Elayne right after she has her kids. It's the one thing I am looking forward to).

12. Cyndane and Moghedien do some bad stuff. Not sure what they could do, but hopefully something. They need to play a bigger role in ToM.

13. Rand gets captured by Tuon and taken to Seanchan to fulfill what she thinks is prophecy. Right after Rand gets captured, Tarmon Gai'don starts.

14. Rand is on another continent and nobody knows where the heck he is except for Moridin and Cyndane (the only two people who can track a ta'veren via ripples in the pattern). Elayne, Min, and Aviendha don't know what has happened only that Rand is far away to the West. Eventually Mat and Perrin finally figure out they might know where Rand is, but by the time they get somebody who is willing to help them stage a rescue it is too late. The swirls change; Rand is whisked away from the Towers of Infamaral by Cyndane and/or Moridin and the swirls now indicate Rand has been taken somewhere else (probably Moridin's fortress in the blight).

15. Tarmon Gai'don starts, AMoL begins, and the good guys realize Rand has been captured by the Shadow. They don't dare a rescue at this point as they are occupied with other things, namely millions of trollocs and Mazrim Taim's army of channelers.

16. Aviendha refuses to give up. Taking the dagger that hides you from the Shadow, accompanied possibly by Moiraine, she attempts to rescue Rand in AMoL. Aviendha and Moiraine succeed. Rand can't believe Moiraine is alive and with the burden of her death lifted from his shoulders, Rand is finally ready to fight the DO. Rand stands, thanks Moiraine for all she has done, asks her to make apologies for him to all those he has hurt and hasn't had a chance to ask forgiveness from, kisses Aviendha, opens a gateway to Thakan'dar and steps through.

17. Aviendha and Moiraine travel back to Caemlyn, where a massive battle is taking place. They step into the thick of it and rejoin the fight.

18. Meanwhile, Rand defeats Moridin and defeats the Dark One, resealing the bore.

That is how I imagine things playing out.