I wouldn't be happy AT ALL. One, that episode felt like it was too rushed. Having twilight as an alicorn and having the spotlight among her friends is bad enough in my opinion, but then to know that the show ends once twilight becomes the princess? When i first watched that episode I had the feeling that hasbro intended that one to be the final episode, especially how twilight flew into screen and said "everything is gonna be alright", but because of the amount of money they made they decided to extend the show and give it a fourth season. Idk if thats actually true but thats what it felt like to me. Im sure alot of other people think this way as well.
Dont get me wrong im glad that there is a season 4 regardless of twilight being a princess and being "more important" then her friends, but i hope they dont mess everything up. I know there is a lot of potential with the story now that twilight got this change but for some reason i think that season 4 is going to revolve around twilight which is something I never wanted. If they actually do that, then they should rename the show "My Little Pony: Twilight and her friends". We'll see what happens i guess