there's a possible intro for Food Chain (see video on the right) and my theory is that after Food Chain airs, i think that the original intro would be updated into this intro, but without the Jake the Caterpillar and Finn the Flower thing, everyone's faces being replaced with Finn or Jake's faces, keep Pendleton Ward as the singer instead of the singer in this intro, and regular animation. another thing the intro would have if it was updated is it would have the other characters in it (i.e. Flame Princess, Abracadaniel, any of the new characters, etc.). again, this is just my theory of what would happen to the original intro. 
Adventure Time - Food Chain Intro In HD00:25

Adventure Time - Food Chain Intro In HD