User blog comment:Jimeee/Skyrim 1.9 beta update adds Legendary difficulty and raises level cap (Updated Apr 8th)/@comment-86.29.125.105-20130304203813/@comment-3496379-20130304210031

Eventually. If I've read the patch notes right, going to a Legendary skill not only returns your perks (much like the Waking Dreams reward from Dragonborn), but it also resets your level in that skill back to 15. It's basically a "back-to-square-one" function.