4. The Doctor Finds A New Body
This is a theory that I've heard quite a few times from quite a few different sources, and I'm not sure why I find it so dark. The idea is that the Doctor would find a new body to transfer his consciousness to. And then he'd carry touring the universe in that new self. It's certainly a novel way to cheat death, but it rings more of the Master than the Doctor. Perhaps then, that's proof of it being a viable option for a darker Doctor? It's reminiscent of the latter seasons of Heroes, where Nathan Petrelli dies, and his family place his consciousness in serial killer Sylar (not before they've wiped his mind, though). Would the Doctor face his body's previous consciousness returning? It's all a bit horror story-esque, but it's a dark path to send the Doctor down...