PBR doesn't necessarily mean path tracing. It basically means leaving behind ad-hoc, phenomenological models like Phong shading, and using models and algorithms with a physical basis behind them, e.g. realistic energy-conserving BRDFs, making sure different components of the lighting equation match (e.g. specular highlights and environment reflections should have the same reflection coefficient), physically correct light attenuation curves, and stuff like that. I wrote a longer post on Gamedev StackExchange about it. This stuff has already taken off in games, as numerous AAA games of the last few years, as well as all the major engines, are doing it.
Path tracing, photon mapping, etc. are eventual goals; sure, it would be great to do that stuff in real time, and people are working toward it but we're not there yet. That doesn't mean you can't still use PBR to good effect in games.
Also, just because the rendering is physically-based doesn't mean the art has to be in a realistic style. People have done and will continue to do stylized or cartoony CGI using physically-based lighting and shading. Look at Monsters University for example. And as the rgba32 blog post pointed out, there's still a lot of room for different styles, moods, etc. based on what you do with the art.
As for hyper-realistic rendered violence (or porn for that matter), that's certainly a debate worth having, but there's no way that it's going to throw up a "legal cloud" around real-time PBR techniques. That makes no sense.