One of the main issue that I see is that vray renders are quite cheap, and usually ( at least where I live ) some guys do this job for around 50-60€ per shot, which is ridiculous considering the amount of work on shaders and lighting.
Archviz in a game engine is something that always interested me and I started quite a bit ago with Lumion, but the lack of “game logic” and the overall price was a big problem, plus the ability to do video only ( now you have a standalone client which you can send ) was a problem.
Honestly UE4 right now is the best solution available, and the quality is simply stunning.
I’m creating a demo right now and I will start to go around and propose this solution and check the response, so hopefully this solution ( together with Oculus rift ) will be the best choice…I also order two mocap suit ( Perception Neuron ) which soon will have UE4 plugin, so I could have both streaming mocap and Oculus together for total immersion, and hopefully blow awway the customer 
What I would like to see is a couple of tutorials Blueprint related such as:
- Material swapping using left-click mouse
- Ability to have two setup ( daytime and nightime ) swappable without too much problems
- A compressed/light .exe to send directly to the customer in order to view the project
- Web browser viewer ( 4.5 has it, right? )
Cheers