It most likely will be Tyler Roehl, if he wants it. Many fans believe he would make a better head coach than he is an OC. His intensity is sky high, and people would run through walls for him. He is the ultimate motivator. As a coordinator, Roehl was in love with A gap power too much, and not opening things up with the passing game like previous coordinators..
While Personally I liked Entz, he did not seem to enjoy dealing with the BS that comes with being a head coach. I'm sure his inbox was full after losing 3 games this season, and people were probably threatening to put FOR SALE signs on his lawn. I'd bet he doesn't even want a head coach job anywhere. Just let him coach a position and make almost a cool million per year sounds pretty good too.
The only other outside name I'd think would be in consideration is Tim Polasek, the OC from Wyoming, and that's if Roehl didn't want the job. I highly doubt Vigen would even be interested.