The market is a very big one, and Epic is advancing in some ways, and other companies are focusing on other markets. Epic’s definitely positioned itself as the next-gen high-end game engine provider, but for older platforms, smaller and simpler games, and the mobile market especially, that’s a different question. Unity has managed to make a very lightweight engine, with a lot of practical uses, for example. Cryengine had a real-time dynamic GI system for years even before hardware RT. Besides, Epic’s innovations will push other companies to try harder, which is better for everybody.
The gap is most certainly closing, I agree, but I think it will remain for just a little bit longer. As ray-tracing hardware is adopted more and more into the mainstream, the basic support for these features will increase. With technology like ReSTIR, a lot of light transport can be done in real time, but you still have to wait for certain types of features like subsurface scattering, volumetric scattering, or caustics. Give it five years though 
AI and the work with NERFs will almost certainly be introduced into the engine at some point. I’ll suppose a member of the Strata team may already be doing experimental work, but time will tell.
And both, effectively. I’m actually back at school to grow my knowledge base, become better with the art side of things.