There's no way he's coming back at this point. As much as it sucks for him to have to take this mindset, he's lucky to even live a semi-normal life at this point. The symptoms that supposedly lasted long after the initial injury sounded awful. He should move on and make the most of what he has, which from what others have posted here is exactly what he's doing.
Considering the way he's dealing with PCS, another hit would finally be it. If he takes another Matt Cooke like hit, stick a fork in him he's done. Best to stay away, he's got 4 mill/yr coming to him for a while, enjoy life, but it sucks he can't play hockey again if he does.
He has no need to play again. Dude has a pretty good life (accept the no hockey thing and the PCS). He's going to sit back, enjoy himself and play a **** load of golf. Dude is a scratch golfer, he could end up playing professionally on the seniors tour.