Personally I don't think the UI should change much in Seven, I also don't see Windows being dumped in favour of a new kernel.. it doesn't make sense..
I don't think Windows is destined to fail at all if it doesn't change, they just need to work on releasing more often and keeping Windows pruned..
The virtualization idea is just one of those things we get attracted to as developers because it looks really clean and a good way to detach from legacy problems.. but it doesn't make sense for the OS to move like this.. the OS needs to provide a better platform for developers, adding features in, more than anything in the next versions of Windows, I want improvements to .NET, and all the foundation systems they introduced with .net 3 fx (whatever it's called!).
You don't think running legacy stuff under virtualisation would allow them to move forward without being hampered by backwards compatibility?
Serious question. I always thought this was why folk were so keen on it.