We are dealing with a Pre-Beta - So there will be inevitably be a lot of Vista references left in the code. I personally think that Seven will be evolutionary rather than revolutionary. Microsoft have given it a Full upgrade identity by naming it Windows 7 but the actual revision 6.1 would suggest that it is an intermediate release. Marketing reasons mean that the public face needs to be Seven but the programmers tend to be a lot more logical about these things than the salesmen so 6.1 is more realistic.
If you look at the transition from Windows 2000, (Windows 5.0), to XP, (Windows 5.1) you see the same thing - and when did you last hear XP called an upgrade or Windows 2000 SP3 or the like.
The amount of changes between Vista and Seven are many and will increase before release - but, unlike the transition from XP to Vista, are not enough at a technical level to see the revision level go from 6.0 to 7.0
Just the way I see it - and I think that after all the bad press about vista I can see the thinking behind both the programmer's and the salespeople's strategy - Hopefully they will get the balance right - so far so good anyway