He ended up bowing out from the game and largely retreating from the tech space entirely. Lotta reasons for that; but mainly -- as a wildly successful entrepreneur he suddenly found himself to be a highly influential figure whose every casual statement caused news article to get written[0] and he DID NOT WANT THAT AT ALL.
True, he made a ridiculous amount of money, but I don't know if it was worth giving up his creativity.
Well, you could always just open a new GitHub account under a new name. Perhaps he's done that.
As for the "Q is legit" statement, he quit Minecraft before Q was a twinkle in 4chan's eye. I don't follow Notch and haven't for years. I'm not surprised a lonely tech enthusiast was ensnared by the Q cult, though.
[0]: https://www.businessinsider.com/minecraft-creators-new-mansi...