I suspect what will happen is he will "retire" from his own murderous behavior, and instead become a spokesperson for other fascists like the one who did the attack and murder a couple days ago in Portland. That could keep him relevant for a loooooong time (maybe not forever, but at least years rather than months).

Sure, but that kind of assumes there is an actual interest in making him stay relevant. He's not exactly a fountain of charisma. He can not fill a position as some kind of unifying force and sooner rather than later it will become convenient to throw him under the bus. Right wing pundits with actual clout and charisma will start to use him as an example of what the right is not, portraying him at first as a dumb kid who got himself involved in a situation he had no business being in and eventually probably calling him a murderer themselves. This will not be "facing justice" or anything like it. The people doing it will be horrid ghouls only in it to seem like the new smart right wing pundit who opposes murder and should therefore be able to support genocide unopposed.

But there is no reason for them to keep him around, and he doesn't have the charisma to defend himself the first time someone tries to rise at his expense. Being the darling of the right at the moment doesn't mean that they actually love him. They will eat him, and I cannot see him getting out of it. That's my prediction anyway, and I kind of hope it's right since he actually is a murderer. I do not look forward to whatever awful thing rises to take his place, just to it stepping on his corpse to do so, which I do think will happen.