I dont think Mac takes a job without knowing the QB situation up front. I dont think you can build around Allen and Cam is as good as gone, I get they have Grier but thats a long shotMy guess is Carolina, because Tepper has those ties to Pittsburgh and MM is a "Pittsburgh Tough" guy which could appeal to Tepper.
As far as the QB situation goes, my feeling is that they will hire the coach first and then (along with the new HC) decide what to do with the QB situation. To me, that order of doing things makes sense regardless of which new HC you hire.
Also, the advantage of hiring MM is that he's available right now, so you get a jump on things and can make some of the other coaching hires as well.