We'll see.

In the context that there would be 3 books, I could imagine Jordan choosing to keep the demise of Graendal for the last one.

However, what we have is three novels that originate from a story designed to be told over one huge novel. Brandon had to make some changes, but he appears to have been very light touched changing stuff RJ had determined. We know he's made some changes even then, in places where Jordan had not decided and left notes about possible options he was considering. Brandon in those places have mostly chosen one of the options, but he also felt Jordan's mind wasn't made and he had the freedom to come with a better option. Well, Harriet did give him that freedom explicitely, but Brandon also felt it was right (and I tend to agree. Stick with RJ for the finalized decisions, but constraining yourself for details just still under consideration would only lead to a bad book).

So... Jordan intended to tell the story in one book. He may not have managed to get it printed as one, but that's immaterial.

In the context of one book, it just doesn't feel right to me that Jordan planned for Graendal to return as an antagonist. We may get to see the ruined Graendal, but no more. It's too late in the game Fionwe. It's too late to involve her with Demandred - give her a place under him. It's too late to give her a place among Moridin's Pets. It's just wasteful, just to make her die later in the book. A broken Graendal would be really boring anyway. There's no time to give her an arc à la Cyndane or Moghedien, no time to go into her hopes to be released etc. Already we know RJ intended to go into some of that with Cyndane. Parading Graendal around would add strictly nothing - there's nothing there we can't imagine ourselves just by telling us she'll be SH's pet.

I know the Shadow has a lost many top agents and could use some more, but that's to be expected in the final book. The time for "they're gone, but not really" is over. About the Forsaken, Brandon said something like "what you see is pretty much what you get" when asked about returning ones and if Mesaana would be saved and such. A fair chunk of the original AMOL has already been devoted to Graendal. The build up wasn't satisfying because Brandon seems fairly uncomfortable with the character in the first place (he had to invent a lot for Rand in TGS and when you can't think much like Graendal, it's not easy to develop a plot for her!) and in the end underused her in Rand's AD storyline. We likely would have seen one or two more scenes along the way with RJ, more hints of her tactics in AD, likely a scene of Aran'gar meddling with a Graendal agent too. Still, it built up to the confrontation with Rand, and her demise as a pet.

So I don't think Jordan had a place for Graendal. We're entering the last act of the last book (in his mind). He's back to his three "core" Forsaken from the early to mid-series: Moridin, Moghedien, Lanfear. His big ace for TG is Demandred. He has a whole cast of "younglings"...Slayer, Alviarin, Taim, Liandrin, Shiaine and Hanlon, to name just a few. In an ironic way, the tables are turned: the Light spent the whole series "training" new leaders and unable to all come together. Now they're all ready to face what's coming through the crucibles of experiences fighting the Shadow and other things, and coming together. The Shadow has rather kept all its "new generation" crushed under the boots of the Forsaken since their awakening. Ishamael had this huge organization, organized in circles and cells, and hearts. Through the series, the Shadow has crushed its underlings further, and constantly eroded what at the beginning of the series stood together. Now it's the eve of TG, the few remaining BA are mostly scattered, and Moridin needs to use his two pets mostly to run around trying to gather and mobilize the DF because the circle organization is by now very undermined.

I think in the LB, we'll see a lot the underlings in play, and they won't manage well to hold the Shadow together. Demandred will start with a bang, but I'd bet the farm that before the end his organization will collapse because he's way too self-centered and egomaniac to be a good leader of men. Demandred isn't a good team player, because he places his ambitions and interests above the common good. I'm sure he's surrounded himself with similar men, like Taim who is just like that. At first it will work and they'll all rejoice in his genius, but the more Demandred's lieutenants gain successes of their own, the more their ego will inflate, and the more they'll be envious of Demandred while they less and less see in what exactly he's supposed to be so great that they couldn't do the same. We won't see much of that, but the theme will be exploited for sure. If any Forsaken falls because of a betrayal from within the Shadow, it will be Demandred. It's either that, or the one guy who appears to more or less manage to keep his envy of Rand, his personal dislike of Rand, his own ambitions in check to the extent he will resist betrayal and grow into a team player (Logain, of course) will be the one to kill Demandred, or be involved with those who will kill him. In his personality (not military skills), Logain has the potential to become a Demandred or to accept his secondary role, make his peace with it, and be rewarded for that by taking over from Rand as the nominal leader of the male channelers in TG, until they fold into one organization with the women.

Anyway.. back to the point. I don't have a strong opinion whether some top DF will be raised to Chosen level or they will get another title but will get some of the prerogatives/the Mark. I think it would be logical, though. Cyndane and Moghedien won't be available for anything but "special missions". Demandred leads the war. In the Trolloc Wars, the Dreadlords couldn't make the Shadowspawn obey them the way the Chosen can. They had to convince them to "play along", which is why after a spectacular start when Ishamael was around to command, the TW petered out after he wasn't and even a massively wounded continent managed to to turn the tide and finally win. For practical reasons alone, introducing a whole new crop of Chosen right before the LB would be a good move for Shai'tan. It would highly motivate the top DF for the LB. It would remind the last three Chosen they must perform and give everything they have too (I exclude the Nae'blis, the dimwit and the sex slave). But most of all, it would simplify logistics, with the new Chosen Marked by the DO and able to coerce the Shadowspawn.

Thematically, it would parallel in the endgame of the Shadow what has gone on in the Light through the whole series, with the "young leaders" rising. The Shadow would rather catapult them at the top at the end, forced to replace Mesaana, Semirhage, the lost generals etc. and this will fail pathetically, the same way the "young heroes" failed in the early days.

Take Alviarin... She could do her job well as a hidden leader, because only three sisters knew her identity and the rest of the troops had to obey without ever knowing who the bosses were. She's not well liked at all in the Tower. She's a cold and arrogant bitch who's full of herself, with very little leadership traits and zero social skills. She's not ready at all to lead the remnants of the Black Ajah in the open. But she will likely have to, with Mesaana gone... We know very well what Alviarin doesn't, we have seen what a group of "open BA" is like (Liandrin's group). In hiding, they're forced to follow orders and have no idea who the leaders are. In the open, they're a contentious lot who constest everything, much worse than the Light's WT factions ever were, they can barely work together.

It's not as bad for the men, as Demandred has created a structure. But it's all a barrack army, wet behind the ears. Tons of training, barely any real field experience (the Asha'man with field experience went with Logain or Rand). They're all content for now with their little bullying over the Lightsiders at the BT, their grand rank names and their little favours. That won't hold long when they go in the field, where the ambitions will be unleashed, when they no longer have anything to gain to help the next guy to shine.

So I'm not convinced there will be new Chosen, but I don't dismiss the possibility (it would work thematically, to officialize their sudden rise in status, like it was through the series for Mat, Perrin, Egwene, Nynaeve, Elayne etc.)

However I'm convinced it was fully intentional on RJ's part to have the Chosen monopolize the top places, and then nearly all vanish right before the LB, leaving a leadership vaccuum that the DO will have to fill at the last minute with individuals quite unprepared for the responsabilities. The sole mystery is whether this will come with a Mark and title or RJ intended to let his Third Age villains as "apprentices" to the end, desperately hoping for a status they'll never get but forced to take on the responsabilities of the Chosen, in effect.

Right now the Shadow has a Rand in Moridin, it has Mat in Demandred. Moridin has two pets, both of whom hate each other and are specialized in TAR like him. That's all that's left.... except all the "apprentices".. Slayer, Alviarin, Taim, Shiaine and so on.

So I really think it was fully intentional to destroy the ranks of the Chosen before TG truly began, to leave that leadership vaccum. IMO, that will include Graendal. Rand's main foe is Moridin, but he will deal with him at first through Cyndane (who I think may also go concurrently against Perrin). Moghedien is finishing the last touches with the agents involved in the battle of Caemlyn, after which I expect Moridin will unleash her on Elayne and Egwene, the rulers (and that bunch) - and until Moghedien is forced to come out of the shadows, she will bite them badly. The "military characters" will have their hands more than full with Demandred alone, as far as Forsaken go.

All the other positions will be filled by Third Age leaders, with or without titles.