Since I already have the 24-105, I'll wait and see how this new lens compares to it. If its noticeably sharper, has better IS, not crazily expensive and doesn't suffer from lens creep (my 24-105 does), then I may switch to it. I also have the 70-200 f4 IS, so I don't mind switching lens as needed.
I'm going to stick to my original plan when it comes to lens, which is to buy the cheaper F4 zooms and supplement with fast primes (1.4 and faster).