Tablets and other portable touchscreen computers are pretty popular nowadays and only becoming more so; companies like Canonical or Microsoft recognize that most people (i.e., ordinary users) want this form factor, and so it is only natural that they develop their OS interfaces to stay with the current trends. I doubt many people would want a tablet with a traditional desktop UI on it. It seems that these people are also trying to maintain a consistent UI across devices, which also makes sense if you look at cloud computing. The idea is that people want a familiar interface on whatever devices they own and to be able to interact with their data in the same way across each of them rather than have to learn a new interface for each device they use.
That all being said, rest assured that I don't think traditional keyboards will be going anywhere anytime soon. Touchscreen computers with dockable keyboards like the ASUS Transformer, for example, show that it is possible to get the best of both worlds. Work on making Unity keyboard-accessible has also been ongoing; see recent additions that will be present in 12.04 like the keyboard shortcut overlay, for example. Not everyone needs to have a keyboard to use their computer, but if you do choose to continue to use one for whatever type of tasks you have, you can bet that it will still be well-supported, at least by Canonical.