During a panel at SXSW today, Gearbox revealed that a new Vault Hunter is coming to Borderlands 2. In a teaser shown at the panel, Gearbox teased that "deep beneath Pandora, an experiment has escaped. Bandits beware, a new Vault Hunter is coming. More mayhem awaits."
For now, additional details (including a release date) haven’t been revealed, though Gearbox franchise director Matt Armstrong added that the content will be part of the Borderlands 2 Season Pass and said that “DLC is announced on a very tight schedule, and I don't think you'll have to wait long until you see that character."

Back in December, Gearbox told IGN that it will continue to support Borderlands 2 with downloadable content, and could even offer an additional content season after the current one concludes. Previously, Gearbox PR and marketing manager Adam Fletcherhinted at “possibilities of incorporating additional characters."
In addition to the three expansions released so far (Captain Scarlett and Her Pirate’s Booty, Mr. Torgue’s Campaign of Carnage and Sir Hammerlock’s Big Game Hunt), Gearbox previously released the Mechromancer class as downloadable content. The current season pass includes at least four add-on campaigns.
Source: Joystiq