For me it can go either way. Would I like one? If they are putting it out there I will take it. Do I need it to continue playing the game? No. Honestly I've barely done everything on even one of my characters.
More than anything I would like to see another character introduced and the ability to add more space to our storage or ammo. But make it ridiculous by charging a full 99 Eridium for any expansion above what the vanilla game had.
There's a dude in the bushes--HE'S GOT A GUN, what's he doin? I don't know I don't know, RED TEAM GO RED TEAM GO!