You mean get the same render in real-time that mental ray gives when you hit render? Not really, otherwise it would just give you that in real-time all the time. You could look into a GPU render to try to get more realtime results with low samples, like Octane, but is there a specific feature that Viewport 2.0 isn't giving you that you want? I wanted to be able to see in viewport the glowing effects that you can see when rendering with Mental-ray.