Sorry, I'm a realist. That's my time estimate for when foveated rendering will likely become mainstream. Sure, there may be a few apps/games that support it sooner, but actually, I think the 5 years prediction is optimistic.
Note that I'm a software developer, with experience creating games. Look at the delay between the release of a new version of DirectX and games which exclusively support that version as a minimum, as an example. I don't think we'll see widespread adoption, until at least 40% of customers have a high-res VR setup and the customers won't be buying high-res headsets until the games support it and customers have video cards that can run it (probably a GTX 1360 card). It's the classic "chicken and egg" scenario.
I hope I'm wrong, but I feel certain that "the end of 2019" is even more optimistic than Pimax's estimate of January '18 for the shipment of the 8K.