He's set up a lot of characters to die or become lesser value soon. So, once he untangles that knot he can begin telling the story from fewer perspectives again, rather than spinning out new narrators. That's one side of the world - and then those people have to die or travel to the side of the world we actually care about. It's going to be a long journey unless he does a time jump. BAsed upon the previous chapters that's unlikely.
I say 2015 for AWoW; 2019/20 for ADoS. I think about 1/4 of AWoW was already drafted when ADwD was published. He pulled a lot of stuff out of the final to shorten the book. That's pretty much everything that's been put out or read at cons.
Warning: Spoiler! (Click to show)
Two Arienne chapters in Westeros, both traveling to JonCon/(f)Aegon; a Tyrion chapter, a Vic chapter, and two Ser Barristan chapters all converging on the battle of Meereen. When done, I imagine that we'll lose Vic and Ser Barristan as narrators whether dead or not. And, the Theon chapter in the North. I think his big nut to crack is the battle of Winterfell.