Interesting to see Twilight as an earth pony. I wonder what that will mean for the show? Will she be the odd one out, an earth pony who is dedicated to magic? If so, exploring the idea of non-unicorn wizards and earth pony ascension in general would be neat. It'd be nice to see her as the underdog and not the one groomed for success and greatness from an early age. Maybe gen. 5 Celestia is completely taken by surprise by Twilight's abilities when she invested to much into unicorns by mistake.
It may even allow the show to deeply explore the use of magical artifacts and runes a lot more since we hardly see any type of spell usage outside of horns. It would allow for further exploration of the lore that generation 4 merely mentions and glosses over. Maybe we get to see the history of alicorns for once. Let's face it, generation 4 has teased Celestia's and Luna's backstories a ton of times, but we never see it in depth.
Regardless, this means a lot of new possibilities never explored directly by the show.