According to a statement from Asus, Intel will be launching refined variants of its 9th Gen Core processors for the 300 series platform very soon. The company stated that “Asus has released BIOS updates for all 300 series motherboards, adding support for the forthcoming 9th Generation Intel Core processors based on new stepping”. You can read the full release here (opens in new tab).
Apparently these chips should be launching some time around Q2 2019, with BIOS updates already available across the majority of Asus’s Z390, H370, B360 and H310 motherboard platforms. These new stepping chips could provide anything between bug fixes, of improvements to the overall architecture, however it's typically something Intel keeps hidden from public view.
Best case scenario is we'll see tighter, and more refined voltage to frequency curves, improving overclocking and stock performance, albeit at somewhat of a minor level.
There's still no word from Intel as to whether this is accurate or not, nor whether we'll be seeing any 10th generation processors on a new 10nm node. It's likely Intel would introduce both a new chipset and a new socket at this point to cater towards the increased power draw and core count of any potential drop in transistor size.