Something like that, I think.
http://www.microsoft.com/xna/
XNA sounds very very good, & could be extremely promising.
The demos look good too, & they were made on things with sub-XBox2 specs.
There are a couple of interesting threads about this at BXB -
http://forums.britxbox.co.uk/viewtopic.php?t=23199
http://forums.britxbox.co.uk/viewtopic.php?t=23236
What I've read, people are thinking that future XBox2 games will work on both XBox 2 & on PCs running Windows Longhorn (& PC games for Longhorn will also run on XBox2).
More standardisation, easier to develop, bigger userbase.....