The Happy Mask Salesman stated that the evil had left the mask (likely because Link kicked the crap out of it,) so even if he put on the mask, it wouldn't possess him. And if it could possess him, it could just get stolen again by someone, like with the Skull Kid.Majora won't come back because the mask salemen had the majora mask at the end MM so there is no way majora can come back unless the mask saleman puts on the mask.
Either way, just because the evil left the mask doesn't mean it's gone. It could easily still be floating around, or waiting to be revived.
Another possibility is a prequel to MM rather that a sequel. Perhaps where you play as Fierce Deity Link? Just a thought.