If you have peeked at the latest HWINFO utility change-info today, you will have noticed an X590 entry. Als it mentioned preliminary sensor monitoring enhancements for 'ASUS ROG ZENITH II and X590' series. 

Now in addition to that, videocardz states that two ASUS employees have confirmed PRIME X590-PRO and ROG STRIX X590-E are being mentioned in confidential documents that they have seen. Interesting right? So we'll head back to what we initially figured, there might be an X590 motherboard series. There was talk about an ASMedia PCH at PCIe 4.0, which could be the difference. But if that is all, it would not warrant a new chipset name IMHO.

As you know, AMD uses the X570's design of the I/O dies of the Ryzen 3000 CPUs. There are a total of 24 PCIe 4.0 lanes on the processors, four of which are reserved for the interlink to the chipset. The X570 has 16 PCIe lanes plus four for the uplink to the processor. Perhaps the new X590 chipset has a full 24 PCIe lanes as that is the only tangible different I think of.

Anything ZENITH II EXTREME, however, is a Threadripper board, that indicates that X599 is in the works. Please take all this with the usual disclaimers etc.

AMD X590 Chipset surfaces again (and X599 as well)