It is a rather brash statement when you look at all those platforms and realise they can all run HTML5 and java. So if I was a devloper and given the processing power now afforded even the average lowest sample in the combined. Well I'd look at the advantage of portability along with removing so much of the platform specifics. So in this situation It would totaly make that the original argument leveriged by Microsoft in this article void.

You could say that most platforms are more powerful than most users actualy needs and use and again end up thinking HTML5/java. Now backend/server wise type applications, now that is another question all together.