I think you are right, at least in the next 10 years they won't change to much.
When you listen to Mark Russinovich in his last interview a few days ago (link) you get the answer. Even Microsoft don't know what's going on inside the
system. It is just to complex. But after that it will change rapidly I think. There is a extreme desire for correct program code and people will even trade performance to get closer.
The question about the time between releases is a very old one. Today no one has a good answer to that. Take a look at OpenOffice, it is free (yes I mean like in free beer) but there are so many people out there that still use version 1.x or 2.x.
just my 2 (euro-)cent
