Why not? As long as you provide backwards compatibility. There's no reason Vista couldn't have been completely modern, with Virtual PC running in the background to handle old applications. This is like how Apple will handle the PPC-Intel transition, with "Rosetta" in the background doing emulation for PPC apps. Apple's OS change was also very well planned-out.
And Microsoft never got a real OS, mainly because of the decision to be compatible with Windows 3.1.
Because when you play that game, what happens when M$ jumps past their competitors? Companies will just keep moving from one IT solution to another.
The best solution is a happy medium, a mix.
Your "Luck" example is very liberal of you. So Microsoft won life's lottery. What about Microsoft Exchange? How did they leverage IBM's stranglehold over business to make Exchange #1?
By leveraging desktops into servers, and the fact that Notes really sucks. But then Exchange really sucks compared to other software out there. It just takes too much Admin time to run it, and you need to buy too many servers to run a large organization.
Once again explain how they leveraged Exchange into the best selling email solution in the world?
I don't see the desktop connection that you claim, but go ahead and expain it. And when you're finished explaining how they leveraged the desktop to win the email server platform...tell me why they aren't winning the firewall/proxy war.