I think it will spike sales wise, regardless of it having more pages and variant covers. Decent artist on the job, plus a writer who has obviously been building towards this with a number of these characters. Then you have some great character dynamics already built in before it starts.
I actually think if Rosenberg starts well on this it could be a huge hit, we already know he actually likes a lot of the characters he's writing here, so the chances are it is going to be a genuine team book rather than just a vehicle for perhaps one individual.
I am genuinely looking forward to it because I think the guy has a real feel for how Claremont wrote the X-Men and he has definitely spent a lot of time setting some of this up.