People will get tired of it if it keeps going. Look at Pokemon... it's still going and some are getting fed up of it. 19 seasons is too much.... MLP doesn't need to be the same and have too many seasons.
I dont remember too much of the G1 movie, but I remember the Grundles and their song scene. When I found the clip I laughed and thought "I remember this." I also recently found out Danny De Vito voiced the Grundle King.
Grundles good.