City Fall-esque Storyline
 

I have a few theories on what leads to this storyline, and what might happen.

* The City Fall arc will start in that spirit quest episode.
* Anton Zeck and Steranko's mutation possibly sets up the City Fall episode(s).
* Agent Bishop is probably the deal with the devil for this series. Replacing Old Hob and Slash on the deal part, but mostly the former. That is, if he appears before then.
* Slash is more willing to team up with the remaining Turtles, for obvious reasons.
* If I'm correct about Karai forming the Mighty Mutanimals, they might have some involvement.