So X-Men: Schism is nearing its end, which is going to lead into the big X-Men: Regenesis push, wherein there's a bunch of different X-Men teams who don't get along very well, and all the rosters will be juggled.
As a result, the flagship title Uncanny X-Men will be renumbered, and since nerds really like to get worked up about that, as if they're not going to revert back to the original numbering when they hit milestones like #600, Marvel is hyping next month's issue as the end of the series. Which it is not. But hey, Mr. Sinister's involved!
Here are some preview pages from Uncanny X-Men #544 from Greg Land.