It looks like Microsoft are accepting job applicants for development of Windows 8 already. Although the core of Windows 8 has probably been underway for some time, it's always interesting to see any hints of public mention:
You can read a little more at Toms Hardware here."For the upcoming version of Windows, new critical features are being worked on including cluster support and support for one way replication. The core engine is also being reworked to provide dramatic performance improvements. We will also soon be starting major improvements for Windows 8 where we will be including innovative features which will revolutionize file access in branch offices."
If you've got what it takes to be the "Lead software development engineering in Test," apply right here. Or you can sit back and wait to see how Windows 8 will develop.