These are not confirmed, but I am told they are what Microsoft is currently considering:
Windows Vista Home Premium Edition => Windows 7 Home Premium Edition
Windows Vista Business Edition => Windows 7 Professional Edition
Windows Vista Ultimate Edition => Windows 7 Ultimate Edition
Does anyone else find it mildly interesting that Microsoft has gone back and renamed Business to Professional, just like it was with good old XP? These three upgrade paths "confirm" two more editions: Home Premium and Professional. These two are the ones that most customers will likely be buying, whereas the average geek will likely go ahead and grab Ultimate. It's not yet clear whether Microsoft will have an upgrade path for XP users, but I would not hold my breath. Currently there is still no word about Starter or Home Basic editions for Windows 7. We'll keep you posted when Microsoft finally does reveal the official edition list.
