Here's my 2 cents as someone pledged on a full 8K-X package:
Chinese products are always unbeatable for the price. There is no way a Western competitor will launch an HMD that is better than 8K-X soon, for the same price, it will have to be more expensive due to R&D and production costs. Prime example - Star VR, which may be 3-5 times the price. Even if they reduced the final cost in a year or so to twice the price, it's still twice the price.
Top end AMD Navi 7nm cards should arrive from AMD by the end of 2019, NVIDIA will have to respond with a 7nm refresh of 2080TI. A 2080TI on 7nm will be an incredible card, irrespective if AMD deliver or not. 2x 2080TI 7nm refresh should be able to run an 8K-X, which is basically two miniature 4K monitors, allegedly at 90hz. We also need to factor in NVIDIA NV-LINK and if Pimax have been talking to Nvidia, which I expect they have, as the more HMD's sold, the more people will then flock to Nvidia products, as NV-LINK is necessary for ultra high resolution VR gaming. AMD also now have their version in the pipeline - xGMI
So for me, if you aren't a regular VR gamer, then I'd stick with your 8K-X pledge. By the time it arrives, watch movies on it for 9 months or so. Later, you can play native 4K per eye VR games once 7nm GPU's emerge. Yes, you may then find someone launches something better, but this is life and also by buying Pimax, you aren't supporting Oculus with their controversial walled garden software platform. which is one core reason people went with a Vive instead of a Rift.
Worst case scenario, keep it boxed, never open it and sell it online for $$$ as until it's sold on the Pimax store, only 400 example will exist in the world and you have an exclusive product.