Most networking companies are being lazy, what is the point of selling 3x3 routers if they are not going to sell 3x3 wifi adapters?
Asus is still the only one with an old 3x3 AC wifi adapter.
Furthermore, 8x8 will not be possible in most of the countries, it will only function in 3rd world countries.
The reason being is that many countries have troll organizations similar to the FCC which create stupid restrictions such as limiting the channels which can be used. for example, on the 5GHz band, we really only have about 4 channels, all of the others have such horrible restrictions that some router companies will not include them, and the ones that do, will pop up a warning if you try to use them because the FCC limits makes those channels slow and unreliable to use.
Going much higher than 5GHz, wil mean that higher performance wifi will require line of sight.
At the moment, 256QAM is already pushing the limits of modern wifi radios, as it requires a low noise floor and a very high signal strength, meaning 256QAM largely already requires line of sight at a range within about 15-20 feet.