Aditya Malhotra, a Program Manager Intern at Microsoft has written the following responsibilities in his profile:
I am working in the Networking group. My responsibilities include: • Evaluating and collating technical and business requirements for developing new networking features in Windows 8 • Designing features, functional specification and prototype for Windows 8

HomeGroup is one of the most important networking feature in Windows 7 and I hope MS would make Home Networking more easier in Windows 8.

Stephen of UX Evangelist has reported that Windows 8 Milestone 1 has been compiled.it seems that Microsoft has already started working on Windows 8, Build Number is Build 7504.0.amdfre.winmain.090528-xxxx ,though it’s still to confirm whether the build is legit or not.It is to note that the earlier builds of Windows has build number of the previous OS so they would represent Windows 8 as Windows 7 in earlier stages.
Here is the screenshot of this build-