DarkObsidian 
Smiling Panzerfuchs 2.0
Well, let me be the asshole of the group for a moment and say that while series like Steven Universe, Adventure Times, and Gravity Falls have also left their mark on cartoon history, and have contributed to future generations, especially because of their contribution to gender and family debates, I doubt if anyone will still remember this and their fandom in a few decades. In particular in terms of the show's impact on their fandom.
Not that I would now claim to be right with this very personal opinion of mine, but somehow I find it very difficult to imagine otherwise. When in a hundred years a person opens a book about cartoon shows in the years between 2010-2020, I don't know if Steven Universe, Adventure Times and Gravity Falls (shows I personally like very much!) will actually be on the first pages. At least they will have a hard time getting past MLP G4. ;-)
Not that I would now claim to be right with this very personal opinion of mine, but somehow I find it very difficult to imagine otherwise. When in a hundred years a person opens a book about cartoon shows in the years between 2010-2020, I don't know if Steven Universe, Adventure Times and Gravity Falls (shows I personally like very much!) will actually be on the first pages. At least they will have a hard time getting past MLP G4. ;-)