The gen-to-gen changes will have plenty of internal updates ranging from security to additional CPU options, display options, and 4G LTE options. HP is claiming its Elite x2 G4 will be the "world's first business detachable with an integrated privacy screen" via Sure View.
https://www.notebookcheck.net/HP-Elite-x2-G4-detachable-will-be-over-two-times-brighter-than-the-Microsoft-Surface-Pro-6.421567.0.html
"limited to a native resolution of 1080p"
Typo, should be 1280.
The specs list the lower resolution displays at 1920 × 1280, which have the same 3:2 aspect ratio as the 3000 × 2000 resolution display.
The page on the HP website implies that this charges the pen by attaching to the tablet chassis now, rather than tucking into the keyboard loop. That would be a really great quality of life update imo. Such a gripe when you go to use it and you're out of battery.
Be interested to know if we get any CPU gains out of this. My one dream for tablet PCs is that we go to a place where you could dock it with an eGPU like some sort of extravagant Nintendo Switch.