I wonder if this will affect sales of the season pass. Probably not but it's stopped me from getting it for now.
Like the original Borderlands before it, Borderlands 2 will have a number of lengthy DLC expansions. The first may be coming from The Workshop, developers of the recently-released PlayStation Move game, Sorcery.
Little is known about the expansion, but as Superannation notes on Kotaku, this "unannounced expansion" promises to have over ten hours of gameplay. As previously announced, each expansion pack will cost $10 but you can also pick up a season pass if you like what you're playing so far.