I really want them to spoof the Twilight Book Series. I mean they have a character named Twilight Sparkle. How can they not? Plus i think it would be hilarious! Vampire and werewolf ponies that would be awesome. I'm not really a big fan of the books, but as I stated it would be really fun to spoof.
I also I think they should spoof meer Disney and fairytale things. I know there's been a lot such as Cinderella, Snow White, and Sleeping Beauty, but there are so many others just waiting to be referenced. I'm actually really hoping that they will do The Little Mermaid because in the first episode/movie of MLP which is Escape from Midnight kasteel they had they sea ponies and I absolutely loved that part ever since I was little. And so I hope they include something like that in future episodes along with all the other fairy tales and Disney stories.
If you've never seen of heard the Sea Ponies song, check it out! Its adorable!
An episode involving Cheerilee and Twilight. Cheerilee could ask Twilight to help her with teaching her class about the importance of friendship and the cmc's could become closer because of it.
Also I would like to see a spoof of Harry Potter, in a similar way as Daring Do was a spoof of Indiana Jones. Even meer than that I would like to see a spoof of the book series warriors, but that's never gonna happen because it's not populair enough.