He still has a pretty solid chance, after all. As long as the next book is finished in a reasonable timeframe and it’s polished enough, we expect that Martin’s fans will be all over it.
From then on, he should be able to get out of his current problematic situation and get back to writing at his standard pace. Of course, some of Martin’s fans are probably painfully aware of how fast he “normally” works, but even the old release schedule was better than what we have today.
Others have been claiming that Martin should look into hiring some help for the next book if he’s struggling to complete it so much, but it’s arguable how much use that would have, and how well it would be received by fans as well.
After all, part of the reason for many people to read Martin’s books is that they were written by Martin himself in the first place, so it wouldn’t make much sense to take that factor away. If anything, we expect that such a move would be suicidal for the popularity of the series.
“A Song of Ice and Fire” has a very strong reputation right now, even in light of all the delays in the last book, and something like this could potentially seriously undermine it. Then again, we trust that Martin knows this better than any of us.