The Surface keyboard has a trackpad. That just moves the problem from hardware to software though. How do you make a single UI that is equally fit for touch and mouse? I doubt that you can. But it probably doesn't matter, touch is going to win and we're going to be stuck with mice being a second class input.
> How do you make a single UI that is equally fit for touch and mouse?
Yep, that's the question I was trying to raise. Having a mouse in addition to a touchscreen not only looks redundant to those who don't need precision clicking, it also causes a potential conflict between different UI paradigms.
When touch is the primary input, every UI element needs to become big enough to touch with fat fingers, so you usually end up with UIs that look like they were designed for kindergarteners. You simplify and hide features until you upset every "power user". When the mouse is the primary input, on the other hand, the added precision allows you to cram more clickable elements into small spaces, possibly freeing up more screen real estate for other things.
Do most functions of most software require precision clicking? Why not just have mouse-specific UI for the particular tasks that benefit from it, and common UI for the rest? This would be similar to how some advanced programs that are basically mouse-driven still have keyboard shortcuts and sometimes even command line consoles, etc., for more advanced usage. I don't think you need an entirely separate UI to achieve this, you can just have certain special widgets, views, "power tools" etc. that act as "mouse shortcuts".
I find most software involves highlighting text. I use the ability to click the space between individual characters quite often. Finger touch plus adjustments with arrow keys gets the job done, but nothing beats the mouse at this for me.
When Windows 95 came out we all had fun trying all the crazy pointer themes it supported (hands, etc.), but I suspect we've all now settled on the fine-tip pointer arrow and I-beam.
