The X590 chipset could be real after all. VideoCardz has gotten its hands on confidential documents from ASUS that mention two X590 motherboards: the PRIME X590-PRO and ROG STRIX X590-E.
It isn’t clear whether these are actually in development or how they would differ from X570 boards, but PCIe 4.0 exclusivity is obviously out. ASUS is also working on a ZENITH II EXTREME, which alludes to another unannounced chipset, X599.
The original rumor was that X590 would support PCIe Gen4, while X570 would retain PCIe Gen3 compatibility. As you know, X570 already supports Gen4, as so do many X470 motherboards. That said we are unsure how different X590 will be from X570. But one could guess that X590 launch will be connected to 16-core Ryzen 9 3950X launch, which is expected in 2 months.