At Gearbox's PAX East panel today, the developers of Borderlands 2 announced that players maxed out at level 50 will finally be able to get to leveling their characters again. As of April 2nd (next week!) you can download what is basically DLC for 11 extra levels (that's up to 61).
But it'll cost you $5 for the add-on, unless you've got that nifty season pass.
The add-on will also come with the return of the Pearlescent weapon type, which was a set of high-level weapon drops and an extremely rare find in Borderlands 1. We haven't seen this weapon type in the sequel yet, but if you download the add-on next week, you might see it pop up here and there if you're lucky to find one of those crafty little guns.