Word has that the beta version will be available around February or March of 2012. This opens the door for a Release Candidate (RC) in June and a possible Gold or RTM build by late Summer, with public availability by October of 2012.
More importantly is not what the actual dates are but what the final user interface looks like. If you don’t have a touch screen then a classic and faithful Windows 7 interface in all aspects is a must as tiles just don’t cut it for most of us. A touch mouse may help, but the lack of a true classic interface and ease of switching from tiles permanently to the familiar desktop interface may make Windows 8 the next Vista as far as user acceptance and sales
For XP users it fairly safe to say that if your favorite applications are not Windows 7 compatible they are not likely to gain new life with Windows 8. For major software companies will this spell the end for XP compatibility? Currently most applications support all three current versions of Windows (XP, Vista and Windows 7).
The beta might give us a real first taste of what software runs in Windows 8 and those that will need a new release of whatever software you are currently using. Office 2010 for example is not really touch oriented so you can expect a new version, Office 2012 perhaps.