It'll be interesting to see how many PS4 users adopt VR once PSVR is out
I'll give you a hint... how many hardware addon's have ever been successful for a console in gaming history? Segacd, 32x, the memory expansion for N64, ps eye, kinect, ps move... i mean really, nothing has ever succeeded in a way that i'd call mass market or mainstream. PSVR will likely be no different. Niche market at best, as VR is likely to end up. A niche product and not much more.
This is just my opinion and I could be wrong of course, but i doubt it. Time will tell.