He confirmed that this upcoming season is his last run. (source)
He says his departure does not mean the show will end. As far as I know, neither the creators nor NBC have made any decisions regarding The Office's future. I imagine it would take a nosedive in quality with such a shift in its dynamic. I wouldn't mind if the show concluded because of this development. I don't particularly like the Michael Scott character as of late, but he's still the primary source of conflict and an integral part of every characters' relationship with one another, even when he's not directly affecting them. He's a piece without which I don't think the machine can function as well.