@sjefdeklerk: sure, others with way more R&D capacity will eventually come to the market, and then make the 8K look obsolete, that's the game. But all the potential products you listed have not been announced for any release so far, so we are left with perhaps, possibly, and your guess is as good as mine as to when these will materialize into a product available for purchase. Will it be 2019, 2020, 2021 ? Given the experience since 2012, when Oculus kicked this industry off (or alive again, if you consider the 90's early try-outs), I am not as optimistic as you are.
Oculus themselves do not seem in a hurry at all. For 2019 I expect them to deliver the Santa Cruz-based high-end stand-alone VR experience. I woud be surprised if we saw the Rift II before 2020.
Apple ? Said to be next year - but what exactly will it be ? I do not see them release any PC-based VR HMD.
Google ? Not even the faintest idea. And will it not go into the same direction as Apple ? They were the first ones to release a sort of consumer AR product with the Google Glass, I would expect them to be looking into a kind of mobile device again. Would seem to fit their philosophy more than a PC-based one.
Kopin ? I did not study them carefully, but thought they are just about increasing the resolution for the (possibly movable) sweet-spot, i.e. mere display-tech ? That would then mean, somebody wouzld have to take that and add it to all the other required elements for a next gen HMD.
So we may well see a well-functioning 8K remain state-of-the-art throughout 2019. And a failing 8K released next month would be second best to the available HDM's right-away if it has substantial flaws.
But I agree that Pimax may still lose significant momentum if the delay drags deliveries into 2019, because some competitors may at least hint at their products for late 2019 or early 2020 and if those promise significantly better performance in some areas compared to the 8K, only the impatient niche of VR enthusiasts may buy the 8K because they do not wish to wait for yet another year.