In one of those things where if it weren't so then something would be amiss in the universe, Gearbox has confirmed plans to continue the Borderlands franchise. Gearbox CEO and president Randy Pitchford said as much at a recent PAX East panel, "It's no secret, obviously there's going to be another Borderlands." Which is good to know.
Now, that's not a lot to go by, but we do know that Mikey Neumann (creative writer on the original and also voice of Scooter) will be heading up the next Borderlands. As to whether or not it will be a straight up sequel or something else we don't know, but with the studio's soon-to-be released Battleborn embracing the whole online-all-the-time thing, the next Borderlands could end up becoming something like a Destiny or a The Division. In that it might take it's action-RPG elements into the MMO realm. Which, would be awesome.