Yeah, he could only finish it in one book if he drastically changed his pacing and dropped tons of side stories. Hell, it will stretch believability for Daenerys to even get to the Seven Kingdoms by the end of the next book, considering it took Tyrion an entire book to get there and he was by himself.
And it took Dany a chapter to sail from Qarth to Astapor. And it took Lil Griff zero chapters to get from over there to Westeros.
It will take how long he thinks it should, you can't point to one trip that was more about what Tyrion was going through internally, introducing some other players, and his whole ordeal of being captured and figuring out a way out, and just extrapolate that to a totally different part of the story. Might as well say just because there was dramatic death at Edmure's wedding there will be dramatic deaths at Joffrey's wedding!
But yeah, there's zero reason he can't wrap up everything in the next TWO THOUSAND FUCKING PAGES. Why are you people talking like he's got one novella to work with? Or, alternatively, why do you seem to think he'll write some 400+ page LAST BATTLE, this isn't Wheel of Time. We rarely get detailed battle descriptions.
There's just some massively retarded reasoning going on here. "It took one character a long time to make a trip, so it WILL take another at least as long!" or "Oh he wrote a lot about Dany, therefor FUCKING DERP". Because you didn't even wrap up that fuckin' thought, Ashin.
Jesus. By all means, spend all day thinking he won't finish ever or it won't be satisfying or whatever. But get the fuck off the idea that it's impossible to wrap up the story in two giant fucking books.
I think that Mereen will end up being VERY fucked up by the battles to come and end up being unlivable. Between Victarion and red priests on Volantis ships, I think that there will be enough ships to head for westeros.
Can't wait! Second read of AFFC really made me want more of those desert fuckers.