Assuming TOE is a TOP (theory of physics), and not the all inclusive thing, then it is possible to theorize about afterlife without having a TOE extant.
Afterlife requires a theory of consciousness, TOC Consciousness is presumably that which survives death. So the requirement, from a physics perspective, is to find a medium that is invisible in which consciousness can exist; and in which your consciousness can exist after death.
I hypothesize that such a medium is a superfluid or Bose-Einstein Condensate BEC or axions or axinos or microleptons (as the Russians call it) or any extremely light (in mass) particle ~ one billionth the electron mass. Such particles, because of being nearly massless, have global size wavefunctions and are superfluids at room and even solar temperatures. Such a medium would be invisible and most likely undetectable. And the physics of such a medium does not require a TOE/TOP. It's all very low temperature phenomena.
The Russians have developed a theory of microleptons. So I do not claim originality. But they have not especially applied it to consciousness. (Ref:
http://www.dhushara.com/pdf/ruquist.pdf.).
To extend this thinking to afterlife, it seems logical to assume that some part of your consciousness when alive is that which persists in the superfluid when dead.
So let's look at our common experience of consciousness. It seems to come in two flavors: waking consciousness and sleeping consciousness. It would appear, and Frolich proposed a theory of consciousness based on this, that waking consciousness requires energy. Energy would not be required in a frictionless superfluid. That then leaves sleeping consciousness as a property of the superfluid if my hypothesis is correct.
Anyway without going on and on, the physics of superfluids are reasonably well understood. So a TOE is unnecessary.
What is needed is to detect such a medium. We can detect EM waves associated with dreaming. But I do not believe that these waves are our consciousness. By the way, what we can detect in the laboratory is at most 5% of what is in the universe according to astronomy. So there must be a great deal of mass and energy available that is invisible in which a superfluid could exist.