Did you even read what I wrote? There hasn't been any significant improvements to sprint, middle distance, or distance spikes in decades.
The only significant improvement has been seen in the recent carbon plate distance flats.
So why are you mentioning spikes? Spikes already have carbon plates and they have limits on total height that would prevent any significant improvements in the future.
Non spiked shoes dont have those limits at this time, so the only way to get a technological benefit from your shoes (compared to runners of the 80s and 90s) would be if sprinters started running in some fancy new sprint flat with no spikes.
But the IAAF is working on total sole height limits. In fact, they started working on that a few years ago, before the 4% came out. So that hypothetical window will close soon.
As long as we are on the topic of the 400m, have you seen the shoes that Michael Johnson ran in? They're practically socks with tiny spikes on the bottom. So despite carbon soled spikes existing since prior to his WR, he still has the 2nd fastest time ever in super thin and flexible spikes.
Nobody who ran slower than him can possibly blame it on the spikes.