Sales will, at some point, start dying. He has, as far as I can tell, relinquished control of the source in a manner that will forbid him from open sourcing the game at that point.
So he can release it as open source, to make good on what? Some "About" page he wrote fucking 4 years ago when Minecraft was nothing but a PC indie sleeper hit?
Get real.
Especially a promise to a community that throws him under the bus whenever something happens they don't like (even if he isn't involved)?
I don't think that is reasonable.