The additional fighters were added in waves shortly after the game's 2012 launch: Tekken Wiki
Finally, the day arrived, and the new character pack was released. The fourth character was revealed to be... Lars Alexandersson, a fan favorite from the previous Tekken games. Fans were thrilled to have another character to add to their roster. Tekken Tag Tournament 2 Dlc Characters Xbox 360
The arcade version of TTT2 (running on Namco's System 369, which was PS3-based architecture) had access to larger storage mediums and easy patching. The Xbox 360 version was squeezed onto a dual-layer DVD (approx. 7.5 GB). The developers barely fit the base game onto the disc. The additional fighters were added in waves shortly