It appears that the latest issue of Game Informer featured an article on The Witcher 2: Assassins of Kings' announced Xbox 360 version, which, according to this Addicted Gamers' summary, contains some new information on it. It seems like Xbox 360 players will get an enhanced edition, complete with four hours of new quests:
As it turns out this new edition of the dark fantasy roleplaying game is the long awaited port to the Xbox 360 which originally had been slated for the fourth quarter of the previous year but has now been pushed back to the second quarter of 2012. The most curious thing of coarse are the details surrounding this new version of the game. Gamers should recall that the original The Witcher also had an enhanced edition that included a significant amount of content ranging from hundreds of game fixes and balances to entirely new NPCs, monsters, and adventures that added hours of additional gameplay. Considering CD Projekt's stated policy to release this content for free for PC users too, this seems like great news all around to me.
This edition seems to be right in line with that. Developer CD Projekt RED has made numerous tweaks and fixes to the original game, further optimized the controls for the console (even though gamepad controls for the PC version were already in good shape), and is said to have added over four hours worth of new quests. The story-arc for these additional quests revolves around the kidnapping of royal heirs which will have the player experience new locations, characters, and dialogue.