It will never reach the level of photo-realism of v-ray that’s 100% sure but I think the other advantages can make up for it (fast and cheap video making, live post-processing and easy VFX viewable in realtime, application making, etc) and there are always ways to fake stuff to look alllllmost as good as what offline ray-tracers can do.
The main disadvantage is reflections/refractions… It’s the most noticeable difference between a v-ray and unreal rendering right now I think. Fake reflections and I think most clients won’t even notice the non-perfectly physical reflections in the scene!!!