Just to be clear, there isn’t much we know for certain about Windows 8. In fact, since the speculated release date is still several years away, even Microsoft isn’t likely to have anything set in stone either. Just keep in mind the long and laborious history of Windows Vista – several prominent features were cut, Microsoft restarted the Vista project at least once and the anticipated date for release was set to be just a few years after Windows XP. Additional information on Microsoft’s Operating Systems can be found in my article entitled: Reviewing Microsoft's Operating Systems - From DOS to Windows 7

Release date – Microsoft seems to be on a 2-3 year cycle with most of it’s products lately. They are definitely pushing for more frequent, less substantial updates. If we go out 3 years from Windows 7’s release date, we’d be looking at late 2012. I am usually pretty optimistic about Microsoft’s Operating Systems, but I’d have to bet it’ll be later than 2012 – maybe 2013. I think Windows 7 will be very successful and will thus afford Microsoft more time to fine tune their next OS.
Architecture speculation – 128-bit support? Some sites are saying a LinkedIn profile showed a Microsoft Researcher was working on 128-bit code base for Windows 8. I know a lot can change in the next three years, but I don’t see this happening. First off, 128-bit processors are still in development (presumably). Developers haven’t latched on to 64-bit processors yet so what is the motivation for Microsoft to support 128-bit architecture? They have better things to work on. Windows 9? Maybe… .Windows 10? Probably… .Windows 8? Unlikely. Improvements – specific improvements can only be speculated – nothing will be set in stone for few years. We can however speculate on areas of focus for Windows 8. Security and Networking seem to pop up in the major tech sites. File systems and file services also seem to be popular areas of speculation based on some recent Microsoft job postings.
User Interface – the user interface improvements going from Vista to 7 were subtle but important. I would expect to see additional user interface improvements, but in my opinion, it’s unlikely we’d see another major shift in graphics (a la Aero) until Windows 9 or later.
Only time will tell what Windows 8 will turn out to be like. Let’s all hope it’s another Windows 7 and not a Vista.