When... (and if) multitouch technology advances so that you can use a pen AND a couple of fingers at the same time, I want to be able to zoom, rotate the canvas, etc. with my hand by using different kind of finger swipes. While still have control of my brush.
Scaling, rotating and moving rulers and stencils would become second nature too.
One could even imagine customizable floaters that would allow you to scale brushsize etc with.
Now, wouldn't that be awesome on a tabletPC or a cintiq (or perhaps the next generation of tablets?).