The question is, whether the brain would reject the body noticing that it is not in its original, or will the body somehow be able to reject the brain...
Theoretically, it is possible- however by that point it would be more plausible to simply replace your old cells with new stem cells allowing for regeneration.
The problem with transplants ( of all natures) is that the body's immune system Is highly selective, however, the body you are being transplanted into doesnot have a brain, meaning that the immune system doesnot work--
In my opinion, regeneration via stem cells is far more likely than brain implants- furthermore if brain implantation was possible I don't see why you would be transplanted into a human, more likely you would be transplanted into a synthetic replica of one ( basically an android)
- Lastly, you also have the question on whether or not humans have souls. If we do, then this may not be possible at all.
-TO OP
- The brains cells do die off after some point in time- as they die off people often loose memory and brain function ( this process is known as brain degeneration) So, even if you transplant your brain, it will still degenerate,- its cells will still die off faster then they regenerate. - That is why I said earlier, that the only "true solution" ( a solution that lasts forever) would be to prevent degeneration and enhance regeneration.