I'd be sorry to see Kieron Gillen leave Uncanny X-Men,
as UXM is my last regular monthly link to the X-Books (AvX and related notwithstanding), and the only reason I'm still reading that is because of Gillen. Of course, it may happen that AvX will end in such a way that I will no longer wish to read any X-Books, so we'll see how that goes.
However, Gillen taking over Iron Man
would be the first thing to make me interested in that character since Civil War