I'm... quite frankly expecting Jake to die. Not that I want hi to die, he's awesome, but he's cupio dissolvi incarnate. All the stuff about aging, and even more than that, how relaxed, even excited he was at the prospect of dying and becoming one with the universe in "The New Frontier" and "Sons of Mars", his surrendering to the element of slime even though he knew the consequences... ok, the last one might not really count, but with the way he's been handled, I don't think death would be an unreasonable finale for Jake.

Also, I take the title to mean the finale will indeed be, as some suggested, about Finn's adventures in Ooo not ending. My personal guess is that he'll travel to all parallel universes (if this does not happen in the next few episodes), maybe with Fern or others, to slay the Lich hand in each of them.