I think the fact that Germany have absolutely demolished Brazil might have put the brakes on any rioting TBH.
I think if this happened early in the tournament then the protests could have ruined the World Cup. But Brazil actually doing so well by actually reaching the semi, and then collapsing so spectacularly could be one of the few things that means the massive riots don't happen.
If they'd gone out in a close game it might have been worse.
I think Brazil might go into mourning rather than rioting mode.