to be perfectly honest, mayhem doesnt need the ufc and the ufc doesnt need him. this is a pretty drastic change in my stance from about 5 or 6 years ago when i was saying they needed to bring him back after his loss to GSP.
he would be hard pressed to find wins against the 185 pounders with decent takedown defense who like to stand and bang (like mark munoz, marquardt, belcher, etc.) and potentially stalled out against the cage by wrestlers with good sub defense. he might pick up some good wins along the way, but he wouldnt contend for a title. fun to watch yes, but worth the money he makes outside the ufc at the moment? probably not.
i think he's one of the few fighters whose personal interest (making dollar bills yo) is best served by staying outside the UFC.