Barnett is still a top 10 guy and has a few good years left in him yet. you can't get rid of a guy just because he couldn't beat cormier. There is a lot of good matches for him should he go the UFC.
I think he still got some fight in him... there are a couple of matches ufc can make with him... look at Mir, I have never seen someone win fights, get his ass kicked, win fights, gets his ass kicked, win fights and he is now fighting for the championship
Anything other then the UFC would be a shame IMO. Barnett lost clearly but still fought his ass off and gave Cormier his toughest fight yet by far. I picked Barnett but that was honestly based on experience I knew going in this was a bad stylistic matchup. I could see Barnett being very competitive in that divison. Barnett skill wise ranks right up there he has quality boxing, good wrestling and his ground game is one of the best. Outside of JDS and Cormier id probably pick Barnett to beat everyone in the divison.