It'll more like be that the web is integrated into applications, as with iTunes, not the way the majority of web applications are today.
He's right about the Windows team bending over backwards to patch stupid application flaws. Why they didn't tell the original developers that they messed up is beyond me. Of course, Apple didn't do either.
The Windows APIs may be dying but it's not dead yet. Besides, there are older APIs still alive.
I would disagree with the amount of "great desktop software" on Windows being larger than on Macintosh. There is more desktop software, but rarely is any of it great, and there is more at the bottom of the pile.
As far as January 1st, 2000, when large machine applications written in COBOL, RPG (II, II), and PL/I weren't converted, they had problems.