No official guidance yet; company will provide more details when ready.
Microsoft released the following statement today from Kevin Kutz, Director, Windows Client, in response to recent speculation on the next version of the Microsoft Windows operating system:
"The launch of Windows Vista was an incredibly exciting moment for our customers and partners around the world, and the company is focused on the value Windows Vista will bring to people today. We are not giving official guidance to the public yet about the next version of Windows, other than that we're working on it. When we are ready, we will provide updates."
News source: Microsoft Presspass