He has. - Edit 1
Before modification by Werthead at 08/12/2009 05:21:36 AM
Arya is in ADWD, so not too long a wait (touch wood) before her next appearance and the resolution of that (and a few other AFFC) cliffhangers. You won't be left hanging for a further x number of years before Book 6 shows up to resolve the Book 4 cliffhangers.
With the exception of Arya's, I thought Martin said he would only include resolutions to the cliffhangers from Feast if time and space permitted. Given the length of the manuscript, to say nothing of the four-year delay, it doesn't seem likely that we'll see resolution for the other cliffhangers (i.e. Cersei's and Brienne's)... unless he's said something different recently, that is.
Arya and Asha are in ADWD as POV characters. Cersei and Sansa have had new material written for Book 6, but apparently GRRM and his publishers have had discussions on including their opening chapters in ADWD, so as to give fans of those characters a little more closure to their stories from AFFC before the next indeterminate length between books. It is possible other AFFC characters may get the same treatment (he wouldn't say anything at all about Brienne, since obviously if he did we'd know if she was alive or dead).
The current situation is that Arya and Asha are definitely in and if ADWD comes in at the desired length (and it's close now), then we may get some Cersei and Sansa chapters and possibly some others from AFFC as well at the end of ADWD. If ADWD gets too long, that's the first material that will go and be held back for Book 6.