Originally Posted by Kotaku
The game’s GI tract says the characters from the original will return as NPCs; enemies will have better AI and interactions (a must after the first game), a weapons overhaul, customisable armaments, and a new currency and resource system
Interesting stuff, sounds promising. Apparently Game Informer will be revealing some more info so I'm going to drop this here. For the moment, the possible "extra links" are grayed out.
Aditional Info @
Game Informer September Cover Reveal: Borderlands 2