I'm gonna assume that the Donald won't even nominate an AG until near the deadline that an Acting can serve. What is that anyway. The confirmation hearings would be a distraction.
Whitaker is already up to speed on everything, DOJ-wise, and is known to be anti-Mueller. He has commented on the legitimacy of Muellers over-reaching scope (into Trump finances).
I think Trump leaves him in place to handle Mueller, and, according to Q's latest, to push the release of previously blocked (by poor [RR] documents and derp dirt.
That's the smart play, at this point.
Trust the Plan.
Bagster