i think he was already working with Dre/Eminem when JMJ died, but i think not having a mentor definitely hurt his music later in his career.I don't think he would have been as successful. I feel like 50 reinventing himself was the cause for his success.
not that it matters, dude got money for life, but... i do think he needed a little guidance on his music after The Massacre, shyt got stagnant.