At the next convention the Adventure Time cast attend, I got some questions that I would recommend. Some maybe answered before then.
1) Is Betty going to have trouble adjusting to her new life style in Ooo.
2) What happened to Marceline's mother? Will we ever see her in some way?
3) Would we see a flashback showing how Marceline got her vampire immortality? Or how she became a vampire if, you put it that way.
4) If Shoko somehow gets revived and turns into a separate character from a past life of Finn, how will she, Finn and PB react?
5) Will there be any references to the plot of Explore the Dungeon Because I Don't Know?
6) After the events of The Cooler, what are the odds that PB will lose her mind? And I mean lost her mind so much, that she "goes mad scientist".
7) What's the secret to Bubblegum's immortality?
8) Is The Litch defeated for good?
9) Are the interactions between BMO and Neptyr considered sibling interactions?
10) How Finn & Jake meet BMO?
That's all I can think of for now.