My brother is *beep* lazy and won't make his thread.
He thinks Chad Michael Murray and Paul Walker look alike, so Chad Michael Murray would fit the role of Brian perfectly. What do you think? I think he would be a great replacement.
They might look alike, but Murray's acting style is VERY different from Walker's. There's no way he fits a role like that. Besides, they would never recast the role. That would be a disgrace to Walker, no matter who they replace him with, and would show that business is more important than human beings. (We sort of know that already, but it's different when the actor dies, even for Hollywood producers.)
Most likely, another character will take his place as the other male lead. My bets lies with Lucas Black's Sean Boswell, who is in the movie already and thereby would be the cheapest solution.