PBR isn't just a feature you "add to a rendering engine" but an entire philosophy how to approach solving rendering problems. This seems to be a common prevailing misconception when people talk about PBR. Quite often people assume that when they have implemented physically based BRDF (e.g. GGX) into their engines, they are "done implementing PBR". They are not - they are barely getting started.
Let's take some of the topics you list and how do you approach implementing them in the "physically based" way.
Depth of Field, Lens Flares, Motion Blur and Bloom & HDR for example. For years these effects have been implemented and slapped as post effect on the screen with some adhoc factors exposed to artists. However, as you know these are effects happening in the camera system and they should be exposed and implemented considering how the light interacts with this system. How camera aperture, shutter speed, ISO, camera sensor and lense system influence the effects and how they should be implemented and controlled considering these physical characteristics of the camera.
This same principle applies to all the aspects of rendering when you go PBR. For example shadows you mention, how would you implement shadows in physically based way? First of all you would have to consider all lights as area light sources as opposed to infinitesimally small lights that people have been doing for ages. Recently there has been push to implement physically based area lights in real-time which is an important step towards more complete PBR, but they are completely omitting proper area shadowing. This is a difficult problem in real-time rendering and there has been only little research done in the area of area shadows. "Real Time Area Lighting - Now and Next" by Sam Martin is a good thing to read if you are interested in the topic.
Talking about dynamic reflections or lighting in general. How should all the different lighting techniques such as SSLR, local/global environment maps, (textured) area lights, SSAO, GI, etc. be implemented and integrated together to form a cohesive lighting system? That you doesn't do double counting and that they are properly accounted in diffuse and specular lighting calculations.
When implementing real-time PBR algorithms, you will eventually have to introduce some bias due to performance constraints and resort to some kind of approximations. But the important thing is that you know what the real result should be and are aware of the compromises you are making. PBR is a paradigm shift from the classic artistic observation-based real-time rendering algorithm development towards more scientific way of solving the rendering problems and this shift in mentality and the direction it pushes you helps you to get more realistic results in the end.