Most vendors have confirmed support for the 9th Gen on X370 and are issuing microcode updates to support. That said most vendors are readying Z390 with ASUS accidentally leaking their range on a post now taken down. We’re it not for AMD committing to AM4 for 7nm Ryzen 2 (3rd Generation) then I reckon you’d be right.
How I see it based on the microcode posted at the Asus forums for Z370s. They all show one 8core code not two.
That makes me think that Intel would push the i9 as Z390 exclusive, leaving i7s to Z370. Is not like Intel hasn't done worse over the recent years. (Z170-270-Z370 anyone?)
That is why also I am holding and haven't moved my main system to X470. (the upstairs system is getting moved from X370 1800X to X399 2950X in september)
If 9900K is supported on the Z370I Strix (I have monoblock no VRM heat issue) then
might consider the CPU (benchmarks pending) until X570 & Ryzen 7 3xxx hits, which I will definitely move over regardless.
Otherwise getting the Gaming 7 with a 2700X in September also.