Liddell has the best chance of doing this since he's getting up there in age.
Franklin/Hughes/Sylvia/Liddell all have really tough fights ahead that put them in great danger of it all being over (not that they can't win it back later tho)
Personally, I don't think retiring with a belt is all that cool. Just keep fighting and let the up and comers earn the belt from the veterans. That's just me tho