I'm slowly going through the Audio series of Wheel of Time, and am currently listening to Lord of Chaos.
Listening to the Audio books gives a different perspective for me, with the books I can tend to skim read, and skip some sections on rereads, whereas with the Audio I can't do so.
Listening to the Dark One's section in Lord of Chaos, and recalling what happened at the end of AMoL, I am wondering if the Dark One really does want to break free or not.
Most of his interactions seem to be there to sow seeds of chaos and strife, and taking great joy in the results.
With the trading of potential futures at the end, Rand was horrified by his own vision of a world without evil, but you would think a world without good could be just as horrifying to the Dark One.
He doesn't seem to be particularly upset about his imprisonment, and for beings like the Dark One and the Creator, you wonder how much physical imprisonment would actually do to them, when they are almost creatures of thought.
Thus, the Dark One potentially has more enjoyment with the world as it is, with both good and evil, and taking satisfaction in causing strife, destroying hope and turning people to evil.
In the earlier books, there are suggestions that the Dark One has actually broken free in the past (tales of the Dark One hunting with his Shadowhounds, the idea of a 'Great Return'
, so potentially he could break free, but sooner or later the Creator would just imprison him again anyway, as he evidently managed to do at least once. This reimprisonment may lead to a different Wheel / set of Ages though.
The Dark One could be creation of the Creator, intentionally designed to introduce evil, so as to introduce the idea of choice and free will in the world (though as per a previous post of mine, I think he could achieve the same by taking himself out of Creation, without requiring the Pattern, which diminishes the degree of choice and free will people have). In this scenario, the Dark One likely accepts this, and certainly none of his plans suggest he wants to take the Creator down.
Thus I think the Dark One sits there, sowing chaos and evil, makes somewhat half-hearted attempts at breaking free, as it could be fun to be free for a while, before it gets boring and he gets imprisoned again anyway. After all, by the time he was battling Rand, did he really think he would succeed, where he had failed many times in the past? It was likely more fun going through the motions, and creating so much strife and suffering in the meantime.
Additionally, we can see instances where the Dark One has successfully taken worlds without breaking free (the parallel world in tGH), and as Mat mentions, even if Rand won, Demandred and co could still have one the big battle, with the Shadow ruling the world, without the Dark One breaking free. While I think this is debatable, with the influence the Pattern wields, it shows that the Pattern will accept some worlds being lost at least, which increases the 'enjoyment' the Dark One can have even while imprisoned.
Ishamael seems to represent this at times as well, with comments of the like of 'we'll keep fighting, but one day I will win', 'the Dark One's return may be in this Age, or another' (upsetting Bors).
While most of the Forsaken are looking forward to the Great Return and the power they will have them, Ishamael always seemed happy with the power he had, and to accept that the Dark One may not break free this age. While AMoL mentions that he came to believe he was the Dark One himself, I think his dialogue with Lews Therin in the prologue of EotW when he was sane was of a similar vein.
Of course, when he came back as Moridin, he had had enough of life at that point, and so began to hope that the Dark One could break free this Age, freeing him from the Wheel, but many of his interactions suggested that while he hoped for this, he didn't really believe this, and may have even overstated his desire for this to help keep Rand concerned.
My apologies for the length of this post, I can't seem to be able to keep these things short 
