There's no way to know whether the next NOOK Tablet will be based on Windows 8, although there's certainly a chance it will be. If it is based on Windows 8 rather than Android, here's how it might work.
Main screen changes
The NOOK's main screen clearly shows its Android heritage, with the largest part of it taken up by a desktop onto which you can place apps and content that you want to quickly access. Tap any to run them or open them. The bottom of the screen offers links and access to books, your library, movies, music, search, and more.
In a Windows 8 NOOK, the main change would likely be the replacement of flat icons for apps and content with live tiles, like in Windows 8 and Windows Phone. So a book library tile might issue book recommendations right on the tile itself. A mail tile would show the most recently received email, just like in Windows 8 and Windows Phone.
In short, the main screen would go from being a static representation of apps you can run or content you can read, into a live, constantly changing environment.
One of the NOOK's niftier features is the ability to share reading with friends, including lending each other books and sharing reviews. Windows 8 would make that a far richer experience.
With Windows 8, you'd be able to receive alerts when friends have new books that they can share with you, or when they've posted comments or reviews. You'd be able to get alerts from your local library when NOOK-lendable books are available. You'd also be able to more easily meld your Facebook and Twitter activities with your NOOK borrowing and lending activities.
Integrating with the cloud
Under Windows 8, the NOOK would become far more integrated with all of your other devices, including your computer, phone, and possibly other tablets as well. Built into Windows 8 is cloud-based integration, especially with SkyDrive. With the new SkyDrive apps, SkyDrive looks and works like a folder on your device, and automatically syncs files everywhere. That means you'd get access to all of your home and work files on your NOOK. You'd be able to read and edit them using the Web version of Office, or possibly a NOOK-specific version of Office.
The NOOK is designed more for reading books and watching TV and video that it is for playing games. But if it were to be Windows 8-based, it would tie into Microsoft's successful Xbox 360 and Xbox Live service. You'd be able to do more than just to see scores and the status of games on your NOOK -- I would also expect there to be a NOOK front-end to let you play games as well.
By tying into Xbox Live, you'd also tie into the service's ability to watch TV, movies, and sports. So you'd be able to go beyond Hulu Plus and Netflix, the primary ways that you watch movies and videos on the NOOK Tablet.
NOOK's software for reading books is superior to the Kindle's. I'm not sure how its features might change under Windows 8, but I would expect it to get a Metro-based change. That may or may not be a good thing; as is, the reader is quite good.
The NOOK Store is a closed system, just like Apple's App Store, and the Windows 8 store. Don't expect that to change under a Windows 8 makeover. But one big change would be that the store would give you access to Metro apps rather than Android apps.
This might or might not be a good thing. The NOOK, like the Kindle, currently doesn't offers a massive selection of apps. I don't expect that to change much over time. But given the Microsoft-Barnes & Noble partnership, I would expect that Microsoft would focus on on having NOOK-specific apps developed.
Will all of this or even any of this happen? Given that no one knows whether there will be a Windows 8 version of the NOOK Tablet, that's hard to say. But it's clear that if there is one, the NOOK Tablet could be improved.
By the way, if you're a NOOK Tablet or NOOK owner, you might want to check out my latest book NOOK Tablet: The Missing Manual.