I don't think his more recent books are less well written as the older books. They're simply different. After all, the central characters used to be lowly ship drivers or below. Most of the story, most of the crux, occured on the gun-boat vs. gunboat level. Now alot of the central figures are major players on the galactic level, wielding entire battlefleets and starsystems. Yes, their's less swashbuckling action, but it's shifted into a far murkier world of politics and strategy, and I'm rather enjoying it.
As to him finishing some of his things up, yes. I see another few main branch HH books before being able to reach a satisfactory end. But he could wrap up the Bahzell books with one more novel comfortably (and should, IMHO.) Simillarly with his Starfire things, he can wrap up some loose ends there.
I'm sure we all worry about another traffic accident or similar, like the one that almost ended his writing career a few years ago with everything left dangling.
Just my 2c.