Loving this series, can't wait for it's return. I think the best course of action for optimus to return (because its going to happen at some point) would be that he comes back to life but leaves to cybertron for some leadership thing there. That would allow prime to be alive and out of limbo (I'm calling it that) and bumblebee can continue his mission on earth with the rest of the crew hunting down the remaning escaped prisoners.