I'll throw a few guys out there that are not already in 40s( hence - career winding down anyway).
Rockhold hasnt made it official but theres no way he should entertain taking another fight in a cage. Hes broken , he had a sucessful career and why add brain trauma ( if he doesn't already have some) to his problems.
Manuwa should not be coming out of his short retirement- why ? I understand he's a fighter with the mentality that accompanies it but lets keep it real. Hes a stand up fighter and much like Luke, I can only see things of a tragic nature happening or leading to it.
Edgar- yes, Frankie. The guy accomplished so much as a clean fighter and pretty much fought close to his walk around weight for most of career. Why let these up and comers use his name as a stepping stone. Hes made plenty of bank and he can retire the right way. His next chapter of his life, I'm sure, will come in the form of still being around the mma world......and for sometime.
Those just off top of my head. This is a brutal and unforgiving game ( and for some , the money that they're actually making - just doesn't add up )