Tough to say. If I had to lean one direction or the other I'd say Frankie has a great chance of beating him, Mendez too, but not quite as much of a chance.
Frankie been in there with the best in both divisions and beaten nearly everyone he's faced. Aside from the first Maynard fight, he's only lost close/razor thin decisions.
On the other hand, either of them is going to have to close the distance on Conor to strike or wrastle with him, and thus are going to run the risk of eating a big time counter on the way in. It also looked like Conor is good at getting back to his feet, which could spell problems.
A lot of ??'s. The only way to know for sure is to see Conor fight an elite wrastler. If he trashes the first one he fights, you can probably say goodbye to the rest of the division.