The thing is that I'd expect foveated rendering to increase latency issues, not help them like it does for bandwidth concerns. During a lag spike you're now looking at an extremely down sampled image instead of what in non foveated rendering had been just as high quality.

Now I also wonder if an ML model could also work to help predict fovea location based on screen content and recent eye trackng data. If the eyes are reading a paragraph, you have a pretty good idea where they're going to go next for instance. That way a latency spike that delays eye tracking updates can be hidden too.