Olive Branch is planning something with trying to get everyone to turn against CelestiaI mean, it'd probably make sense if there was some end goal for him to achieve other than "make the ruler look bad".
Said plan has to do with DiscordHe's mentioned a few times throughout the story, and it could be considered foreshadowing... Also, Olive Branch is attempting to have a rebellion of sorts. And what do Rebellions usually cause? Chaos.
If this happens and Discord breaks free, he'll pull an Eviler than Thou on Olive and become the Big BadHe's also the last villain to have the Elements be used on, and one of Rainbow Dash's worries when she talked with Soarin' was that the Elements might have not worked, what with what happened before. It might be used to produce some final closure on that matter.
Alternatively, Olive Branch is doing this as a Roaring Rampage of Revenge against CelestiaSomething must have happened during the Changeling invasion that caused Olive to become jaded enough to attack Celestia. Perhaps he lost a loved one?
Pinkie and Scootaloo's storylines will intertwine.Specifically, when Speedy Delivery is outed as abusing Scoots, it will cause Clyde to have a Jerkass Realization in regards to how he treated Pinkie.
Olive Branch, Speedy Delivery and Quick Delivery will be executed.They are participating in a plan to overthrow the legal government of Equestria. If that's not high treason, I don't know what is.
Alternativly, they'll be banished..."Well that's not so bad compared to-" "To the sun!"