That scenario does seem very likely. I guess it will be an interesting story arc if it happens.

Maybe we're looking at this wrong.

Maybe Haruto doesn't go into despair. Maybe the Phantoms force everyone else around him to, pushing them to the brink, and he can't do anything to stop it. This breaks him. Not into despair like the Phantoms wanted.. but a new power. The Ultimate Power of the Wizard unleashing his Final Form. That I would watch.

A deus ex machina?
No, please.

Ah so we're back to normal :lol Why not a Deus?

Because, it's a horrible story. Haruto breaking down into despair (With us already knowing he and Dragon don't get along), instead of spawning the Dragon Phantom, gets a new power?
I'd take casual use of Merry Christmas over that.

Or we get Wizard Phantom Style... The Dragon becomes a full phantom but is still stuck in Haruto's body. Think PuToTyranno.

Maybe that's what the Infinity form [citation needed] will be? A form where Wizardragon takes full control of Haruto until something forces him to cool down or he collapses (like OOO PuToTyra Combo at first). Then Haruto gets the Final [citation needed] form when he finally tames Wizardragon after it's become a full-fledged Phantom.