He was wrong about Microsoft's death but correct about how AJAX making web apps feel more desktop-like would remove Microsoft's dominance in many categories and niches.
As a bit of trivia (because web apps have clearly outpaced native/desktop for a long while now), who was it that invented the XMLHttpRequest that formed the basis for AJAX?
The Outlook Web team @ Microsoft; it shipped with IE5.
I have a very complicated history with Microsoft products, but they have introduced a lot of technologies over the years that we all use, even die-hard MS haters.