I am not a believer, but pray that whichever $DEITY is watching over Donald Knuth allows him a healthy and long life to reach the achievement of finishing volume 7.
I think there's a proof that he can at best asymptotically approach volume 7.
What he needs to do is start sketching the rest so that it can be finished after his death in his vision.
He's a Christian (he's also written about that), but considering the time volume 4 took (and is still taking), I have my doubts he's going to make it.