It's not as if we want him to churn them out faster to maximize his productivity. We just don't want the books left unwritten when he dies!
I firmly believe that it's better to not release something unless you're really happy with it even if that means delays. For example, I hate the modern trend of pushing out unfinished broken games and spending the next couple years patching issues that should never have shipped. I hate it when studio imposed schedules driven by marketing concerns compromise the quality of movies and television series.
That said, 12 years without progress is a very long time and the man doesn't have much time left. He's been working on this story for over 30 years. I don't know what's holding him up, but getting an author-approved conclusion written by others (even if only as a backup) would be better than the random fan fic we'll be stuck with if he leaves this world without finishing the final two books on his own.
Look, either he does them, or the publishing house will do some bullshit where a bunch of ... paid ghostwriters "examine his notes" and produce the books.
Noooo that wouldn't happen.... (looks at Frank Herbert, JRR Tolkien)
...Absolutely would / will happen.