Nondh

Correct me if I'm wrong. But I'm pretty sure in the 4th film Fast and Furious. Dom is trying to track down who installed Green Nitrous, he tracks a guy down in a garage. That's Leon, now after Dom nearly drops a motor onto Leon for Information, we never see him again. But from that interaction, Leon has moved on and says this isn't his neighborhood anymore.

I think bring Brian back, through the use of his Brother would be the perfect way to wrap up the franchise