So, those of you who have seen this website, http://www.awn.com/news/voice-acting/neil-patrick-harris-donald-glover-head-adventure-time know that it says that the story of Fionna and Cake will be a saga. Now, I don't think this means they will have one more episode and then Fionna and Cake are gone, but I do think it means that they will have another episode relating to a theme from the first two.
"Fionna and Cake" was about Fionna's crush on Prince Gumball. "Bad Little Boy" was about Marshall Lee flirting with Fionna. Will "Insert title of next Fionna and Cake" be about Flame Prince? Maybe. It makes sense to me. What do you guys think? Personally, I don't give a plop about Fionna and Cake. I like the episodes but I don't obsess over them. But others seem to love it, so I wanted to hear their opinions.