User blog comment:D. Cello/New Assassin's Creed game, "Brotherhood", confirmed/@comment-94.8.38.103-20100507194102

I'm guessing since this is said to be a spin off game, it'll probably use the same engine and gameplay style but with a little difference such as maybe a new level to the gameplay, in this case multiplayer and I'm gonna guess a few more new things. And since it involves Ezio, they've probably developed AC 2 and Brotherhood together.