If what Marvel has been quoted as saying is any indication, Prof. X WILL NOT be back in the comics.
At least not for a few years. I've become distrustful any time they say someone will not return from the dead with the history they have with keeping that promise.
Extended history? Yes, I agree.
Recently, however, they have killed off characters, Nightcrawler for example, and have promised to keep them dead for an extended period of time (its funny even reading that back), and I hope it stays that way.
Although, they did bring in AoA Nightcrawler...but that's a bit different. AoA Nightcrawler is a much bigger badass, IMO, than the 616 version.
We'll just have to wait and see.