Super Sonic needs the elements? Why? He just needs the Chaos Emeralds (Which are more powerful then the Elements of Harmony.) Especially considering the Master Emerald that Knuckles Guards. For those who don't know... the Master Emerald is a source of INFINITE energy.
I think they're facing a more powerful version of an old Equestrian villain, or a powerful robot created by Eggman, or a godlike monster. Whatever they're up against, it's going to be an epic fight to end all fights!