Let's keep it simple. There's a job posting over at the Telltale Games website. Said job posting is looking for a bright-eyed, bushy-tailed Xbox 360 programmer. Said programmer is desired to move an existing engine and art assets to the Xbox 360. Finally, said programmer must have a "love of adventure games." Put it all together and you get Sam & Max on the Xbox 360. We'll note (as did Joystiq's lovable Ludwig Kietzmann) that Telltale's current Sam & Max adventures are episodic, making them a good fit for Xbox Live Arcade.
Granted, it's all speculation at this point -- many things are these days -- but it seems like good speculation so far. If nothing else, at least this points to some adventure games coming to the Xbox 360, an idea with which we are thrilled.