If the Ubuntu mobile/touch devices become popular, I have no doubt that we'll come out with a product for writing Ubuntu mobile apps as well.
We're always looking into supporting other mobile platforms.
We've just pushed all of our MonoDevelop source code to public github and I'm sure that the Ubuntu packagers will be packaging it for Ubuntu very soon.
The new Studio looks great, but there isn't a Linux version. This makes me very, very sad.
The one thing that could make me very happy, however, is if they target the Ubuntu mobile/touch SDK in the future. Wonder if this is on the horizon?