What I think about OOO is the plots going to be unexpected, common what's the point if everyone knows the plot, it's going to be spoiled, anyway I'm still going to have a guess.
Clearly OOO has his Tatoba, Gatakiriba, Ratoratah and Sagozo combo. There are still the full blue (Mezeru) and full red (Ankh) forms yet to be released. Since Mezery is so clever and cunning, when OOO obtains the form, he will go evil (not mad like FangJoker), and then he might eliminate Uva and Kazari (possibly? and there are still multiple copies of insect and cat medals out there), and then he defeats Ankh (again this is not likely to happen until the end of the series). But somehow Ankh wants to help Eiji and gives him the Peacock and Condor medals (let's say he retrieved his greeed form), and this letting OOO 'evolve' into final form.
There's the combo sound of OOO full red form already, see this video:
[ame="http://www.youtube.com/watch?v=2EJHCzsHtak&feature=player_embedded"]http://www.youtube.com/watch?v=2EJHCzsHtak&feature=player_embedded[/ame]