I'd personally like to see an episode that goes really in-depth about magic and its full potential, and the magic behind the Elements, perhaps.
That, along with more of Equestria's history, would make Season 3 pretty damn awesome for me.
I'm incredibly interested in the magic. I personally think there haven't been enough experimentation with it yet. We've seen a few interesting things Twilight can do, but along with the Elements it increases the curiosity. I get the feeling this generation of Element holders should learn and unlock the secrets of its power.
As for history, there are only a few things I want explained. Namely regarding Celestia and Luna, the Discord era, and something else I'm trying to remember. I enjoy having roads opened up to understanding characters and their backgrounds better. Speaking of that, perhaps more of the main six's past. Showing them grow up a bit, or having particular events that shaped more than just their cutie mark futures.
The couple things I really want done would make Season Three amazing for me, but I really just want another happy and exciting season with a continuation and less tragedy/painful-to-watch episodes. I prefer to assume Season Three isn't the final season, with or without 26 episodes. The few spoilers that I've unfortunately seen tell me there could be many interesting moments and I can't wait for Hasbro/The Hub to announce it (and then we wait four more weeks till its premiere).
I really want unexpected episodes, events and situations along with the few things that I want to happen.
