Even though there have been Windows tablets/slates/convertables for many years, I really hope that the the new versions should not lose pen input. I just won't buy a tablet that can't run applications like OneNote. Yes it is great that you can use your finger to do finger paintings, but if you have used OneNote for any amount of time then you realize how inportant pen input is.
The reason I thought of this is because was just going through many years of notes I have taken on OneNote, mostly technical drawings related to visualizing 3D collision detection algorithms etc. There is nothing like having the ability to have "endless paper" that allows you to make detailed drawings. In past of course, I used physical pen/paper, but using OneNote for this is dramatically better. I really hope MS doesn't cave and eventually release a tablet OS that is so dumbed down that it loses pen input. That will be a sad day. Multi-touch and pen input.
This is an area that MS can have an advantage over iPad. The iPad completely excludes these types of applications.
I still believe the best solution would be a new framework based on Silverlight/XNA that can run as either the main UI on lower powered devices (a la WP7), and also as a full-screen app (like WMC does) on more powerful devices on top of Win 7. It should also have a unified app store where developers can target any combination of WP7 and this tablet UI. We know the development tools can already do this (single app targetting WP7/Xbox/PC).