User blog comment:Jimeee/Skyrim 1.9 beta update adds Legendary difficulty and raises level cap (Updated Apr 8th)/@comment-64.121.168.59-20130309210752/@comment-3152761-20130310011612

If you have the PC version you can opt into the beta by right clicking the game in steam and  going into Properties>Betas (I think, if not just look around in there.) If your going to be doing it, disable your mods as it could potentially corrupt games.