He doesn't necessarily have to. When Alicia Keys joined Blackberry as their Creative Director, she still kept touring ;-) (More seriously, Matz joined Heroku but I think is still at Rakuten as well?)

He will be "in the office" though:

John will be working from the new Oculus Dallas office that we’re opening soon.

.. so the likelihood of him spending a lot less time at id, if he stays on there, seems high to me.

He talked in his Quakecon keynote about being too uninvolved in Armadillo because he was working at id/Bethesda. Splitting his time three ways would only seem to exacerbate the problem.

It's been four years since id was purchased. Maybe he's just moving on.

He is not.

"Although Carmack will take on a new role with Oculus, the game designer will remain with id. "John has long been interested in the work at Oculus VR and wishes to spend time on that project," reads a statement from video game publisher Bethesda Softworks, whose parent company ZeniMax acquired id Software in 2009. "The technical leadership he provides for games in development at id Software is unaffected." [1]

1. http://www.usatoday.com/story/tech/gaming/2013/08/07/john-ca...