The final DLC pack is the fifth installment in the Headhunter series, officially called Sir Hammerlock Versus the Son of Crawmerax. It's available today for Xbox 360, PlayStation 3, and PC/Mac through Steam for $2.99 / GBP £2.39 / EUR €2,99.
In the DLC, you'll join Sir Hammerlock along with Brick, Mordecai, and Lilith on Wam Bam Island in the "biggest Headhunter add-on in the series." At the end of the content, you'll square off against Crawmerax Jr., son of the the crab worm from The Secret Armory of General Knoxx from the original Borderlands game.
During a panel at PAX East this past weekend, Gearbox said that though Sir Hammerlock Versus the Son of Crawmerax is the final expansion for Borderlands 2, the studio will continue to support the game through general updates. No new content is in the works, though.
Gearbox is currently working alongside 2K Australia on Borderlands: The Pre-Sequel for Xbox 360, PlayStation 3, and PC. The studio is also working on unannounced new games for next-generation consoles. Gearbox president Randy Pitchford said recently that the studio will "probably" have a new game for new consoles to announce as early as later this year.