Interesting as Samsung developed a 8GB LPDDR4 memory chip back in 2013 - https://news.samsung.com/global/samsung-develops-industrys-f...
Looking at Micron (who probably tickd the box on price to make this happen), they can do 16Gb modules. So that may well happen. However the power aspect as already indicated from the 4Gb to 8Gb, considerations will prove more interesting.
Biggest gain though is more focus upon 64bit, which goes hand in hand with that extra memory.
You have to wonder why they deviated from what I thought was a universal custom.
The confusion comes when you blur the distinction between chips and modules as they do in mobile. They either use single package modules created from multiple chips via 3D die stacking or they use single chip modules.
The custom of using bytes only applies when specifying higher-level computer components.
All other SBCs in this market segments have also been capped at 4GB - I'm hopeful about this leading to larger memory options from other vendors as well before long.
Great of RPi to keep pushing the envelope.