OpenGL support in VR on windows?

Hi,

I just found out that Unity 5.5 only supports OpenVR in combination with the DX11 rendering backend. Does
anyone know if OpenVR support under OpenGL is planned? I'm trying to include an external OpenGL renderer in Unity as native rendering plugin.

If anyone here is familiar with the SteamVR plugin
https://github.com/ValveSoftware/openvr/tree/master/unity_package/Assets/SteamVR,
do you think OpenGL support could be added with reasonable effort?

Thanks!