I've theorized in the past that T'A'R will play a big role, and that Lews Therins' mistake might very well have been the possibility that he placed the Seal on the Dark Ones' prison in the real world rather than the place where the real world meets all possible realities. I also think that Egwene has been studying this, and while she is much more powerful in the Dreamworld then Perrin is, these two characters will be needed to assist Rand in the world of dreams.