Following yesterday's positive comments from the Take-Two conference call, a sequel to the fastest-selling new IP of 2009 certainly seems like a natural next step. However, considering a world is considerably larger than a land ... or region, Gearbox could be planning something appropriately larger in scope than the series' first installment. Or, it could simply be covering its titular bases, as appears to be the case with the "War Hero" trademarks filed earlier this year.
Update: Apparently, the Borderworlds trademark was filed back in 2007. Apologies for the confusion!