Higher resolution and higher refresh rates are still needed for VR. VR requires both a relatively high refresh rate (90Hz) and pretty high resolutions (current generation devices are 2160x1200). I believe that uses most of the bandwidth of HDMI 1.3, I'm not sure if any headsets use HDMI 2.0 yet.

And if you've tried VR, we're still at the point where pixels are obvious and higher densities would be an improvement. The usual comment I get when friends try my Vive is that it looks like an N64.