microsoft prepares first pre-betas of "Windows 8". Ships next year.. so you might want to skip Win7.

( link to pix below , bottom ) .

be aware that if you are upgrading to Windows 7, you might find yourself as soon as next year again in the situation to upgrade to the then-new "Windows 8" once more..

Customers are a constant cash-cow for Microsoft - you should notice that as soon as possible. ( New Win = new Office = new Servers .. new apps = need to buy all the basics over and over again.. that is the game )

So, however Win8 ( yes they now are using only these Numbers.. ) first screenshots are around, they are genuine, leaked by russian OEM that has access to the isos from Microsofts Beta site. The already "METRO" ( new theme name, similar theme like in Windows Phone OS ) branded installation screen shows that Microsoft is doing fast forward development and the Beta/RC phase will be not very far away.
Major Antivirus companies have been delivered with builds to test their AV-apps compatibilty with Win8, indicating that "the mjor OS" is halfway ready already-- otherwise testing kernel-drivers would be irrelevant. If you want : the "underpinnings" are done, now is the UI stuff and the apps.

This indicates a 2012 release seeing more and more screens leaking ( expect isos,product keys also to pop up here and there on the net - it has always been the case in early Windows development ).

What it will be : Well, natural WIndows7 of course. Tighter integration of Windows Live/Skydrive ( "cloud" ) services. Rumor has it that such authentication is needed to operate it, e.g. it is the first Windows that will only function with constantly internet connection, at least all your data will be in the cloud if this goes for real.

Better tablet support, builds for the ARM cpu to port it over to smartphones and thin-clients alike.

Here for your viewing pleasure ( click pics = slideshow of Upgrading process from within Win7 ) :

[link to winfuture.de]