I'd be confident Winds of Winter will be done in a few years, before they get to the AFFC/ADWD season. He already had some of it written before ADWD was out, and it seems like he knows where he's going with that book.
However, I'm worried about A Dream of Spring, big time. He only has about 5 years, tops, to start and finish that before they're at that book in the seasons. That, as the ending to the whole series, will be a huge labour to tie up everything and end every story arc left. I just hope to christ he really decides what he's going to do plot wise in ADOS while writing TWOW, so it's just the prose he's got to work on. It's the only way I can see it being finished in time.
However, I'm worried about A Dream of Spring, big time. He only has about 5 years, tops, to start and finish that before they're at that book in the seasons. That, as the ending to the whole series, will be a huge labour to tie up everything and end every story arc left. I just hope to christ he really decides what he's going to do plot wise in ADOS while writing TWOW, so it's just the prose he's got to work on. It's the only way I can see it being finished in time.