Windows Seven, should be renamed Windows. Just simply Windows. No suffix. No XP, no Vista, no codenames, no numbers. Just simply Windows. This OS is by far the best I have used. Sure it has some bugs here and there, but that's what happens with Betas.
It could be:
Windows Home Premium
Just like when movies are named after their first. Rambo 4 was just Rambo. Rocky 6 was simply Rocky. For games Test Drive 7 was just called Test Drive.
I just personally think it would be cool. Kind of epic in a dorky kind of way. Make this the new definitive Windows. All future installations shall build upon this.