Gearbox announced a November 20 mac release for Boderlands 2 on twitter yesterday:
Surprise! Borderlands 2 is coming to Mac on November 20
Mac users are not always acknowledged by developers as it is a smaller market but still mac users showed their support by retweeting the post 400 times and favoriting it a 100 times.
Along with the announcement, Gearbox also twittered the link which leads to GameAgent, where further information about the release can be found. Aspyr Media are the force behind making Boderlands 2 another addition to the list of mac games. The game will be available on Steam on the 20th with a price tag of $59.99 and on the Mac App Store later this year. You can also get a boxed version before Christmas.
All the current DLC for Boderlands 2 will be made available for the mac as well as all the future DLC. Multiplayer can be played with PC users as well as other Mac users.