Myself, I hope he stays retired as a Legend! Yes, he could come back! BUT,as you age injuries become more chronic and last longer. Even with trg there becomes a diminishing returns with extreme training because of the aging factors.
The fight game concussions are common and GSP has had a few, I am sure he suffered a mild one last night to add to the others. Concussion injuries are cumulative and come back to haunt you. All his joints injuries including his well known knee injury will start to become more and more chronic and arthritic with time!
Its probably also time to explore other parts of his life, we’ll see! He certainly has been one of the best fighters of his sport and weight class!!
Seito Bugei Juku 