4 GB RAM limit

[DrYak]

It's possible in a year or 2, a new SoC can be used for a new Pine64 laptop, (Pinebook Pro II?), that would support more memory.

Indeed, and the recently announced Quartz is a (very) first step in that direction. Though that one, the RK3566 is more middle-line SoC and is probably going to end up in potential successors of the PinePhone and/or PineTab (as hinted in the blog post).
Probably some high range SoC (RK3588 ? Or whatever ends up in the RockPro64 successor) is eventually going to make its way into the PBP successor, eventually.