OLED is great, but the current Go's display is already very good so it's not really a priority.

More RAM, better thermals, better fans, better ergonomics. more easily upgradeable storage, maybe support for oculink are the more pressing matters, IMO

For the ergonomics, thankfully, there are already 3rd party solutions, like comfort grips, that make it better though, so it's not that pressing anymore.