We have already reached the transplantation of the brain. It's risky of course, but once you need to try. There are a lot of nuances in the preparation and selection of the right head. The main thing is that everything is properly sewn up and a new brain normally reacts to a new body.
The brain is not transplanted. Transplanted head completely. Soon to kill a man will need to make a headshot to destroy the brain. Like in a scary movie. The streets will be walking Frankensteins and zombies. I don't want to live in such a world.