I want the main cast to be unique characters instead of remade Gen4 ones, but I still expect them to be mostly ponies. It will be nice if side characters and even antagonists get more character development and have episodes focused on them. World exploration is a must, especially if, like announced, we'll see the future of Gen4 Equestria. Some subtle references to Gen4 would be fine, but I hope they'll make them in a way that won't demand new fans to be familiar with every aspect of FiM.
Things I don't want to see: humans (a big "nope!"); modern technologies, although an early XX century level of technology would be fine; simplistic characters made with "children aren't very smart" mindset. And most of all I don't want to see virtue signaling: I'd like to see new places and fantasy races and cultures, I'd love to see openly non-straight characters, I expect to see some topics that are traditionally labeled political, but I'll hate it if the show is preachy and focused on ticking all checkboxes needed to be called "progressive" just for the sake of it.