The game allows gamers to play a "tongue-in-cheek take on all four cinematic adventures," including the latest film in the franchise, Indiana Jones and the Kingdom of the Crystal Skull, which was not included in the previous game.
Presumably the gameplay will consist of the same drop in/out co-op play which has become a staple of the series. As of yet, the only new feature announced for the game is a level creator.
The levels from the original game will be tweaked, and new ones will be added, eg. the Shanghai car chase from The Temple of Doom, presumably to be added into the Shanghai Showdown level.