Gearbox has just released the Ultimate Vault Hunter Upgrade Pack for Borderlands 2, which raises the game's level cap from 50 to 61, and unlocks a New Game++ mode called Ultimate Vault Hunter Mode, which adds even more difficult enemies and higher level items including a new Pearlescent weapons tier.
Image of a couple of the Pearlescent items can be seen below. Behold the majesty of its ridiculous and awe-inspiring damage. Be sure to keep an eye out for the items that come in aquamarine text, as they're the Pearlescent-tier items you'll want to get your hands on. The new tier of items is rarest in the game with stats that dwarf those of Legendary items.
It's available for $5 or 400 MS Points if you're playing the game on the Xbox 360. It's also available for free as a part of the Borderlands 2 Season Pass if you picked that up.
UPDATE:
In addition to this new pack, Gearbox plans to release the Psycho character pack this May, adding an all new playable character to the game. His name is Krieg and we talked about him here. The game will see its final campaign DLC in June, details of which have not yet been released.