Oh man...
spoilers:end of spoilers
I think there's also a good chance he had his mind uploaded into Metalhead before he expired. IDW has always kept Bebop and Rocksteady as dumb and goofy but paired it with a sadistic and brutal streak in this incarnation. "Didya expect it to look like THAT under there?" "Gross" sums them up perfectly.
But let's not miss that a lot else happened in this issue: We also saw Fugitoid win against Krang and reunite with the Neutrinos. Will Bunrow island become a home for the Utrons, only under the eye of the Fugitoid, so they will be a benevolent force as in the Mirage comics? Baxter saved Shredder, while Koya and Bludgeon failed, Karai seemed to actually hesitate at Splinter's offer to team up with him to reform the Foot.
Leo is going to feel deep guilt over how his plan turned out for Don. And yes, I can see Raph, along with Casey, Angel and Alopex, all looking for revenge. Can't wait.