I asked about this a few months ago, now at GDC 2019 it’s making more and more real the fact that Foveated Rendering is a must and can save us tons of processing power and miliseconds even in non-eye-tracked HMD’s as Fixed Foveated Rendering, it IS possible right now with the oculus SDK, but we need it for the VIVE Pro.
if you have a Vive Pro Eye headset then Eye-tracked Foveated Rendering is now available with Unreal Engine.
At the moment you need to use a custom modified version of Unreal Engine of versions 4.21 or 4.23 but as HTC Vive we are working together with Nvidia and Epic Games towards an integration so eventually you will only need a plugin to enable this.