I hear there's a third preview of S7 out there. If the opening episode isn't a two-parter, that must mean it's as spoiled now as Rainbow Rocks was before its release.
Nah, I'll manage. S7 E1 "Celestial Advice" "Twilight Sparkle agonizes over Starlight Glimmer’s future and receives some much-needed advice from her very own mentor – Princess Celestia."
Trust me, the trailer shows something based on this premise that is bound to get even you pretty mad.