As far as increased density goes, it looks like Samsung will be mass-producting 24 GB LPDDR5x RAM chips* in 2022; 32 GB chips* won't be available until 2024-2025 (see this article, published April 14, 2022:
https://www.tomshardware.com/news/amd-and-samsung-webinar-talks-raphael-overclocking-ddr5-future ).
[*More technically, from what I understand, what I'm calling a chip is actually a stack: The chips will be 24 Gb; with 8 chips to a stack, this gives 24 GB.]
Those should be available for the 2023 MacBook Pro and Studio and, if used, would increase maximum memory for the Pro/Max/Ultra from 32/64/128 GB to 48/96/192 GB. [I think the Pro/Max/Ultra use 2/4/8 RAM chips respectively, and that the chip sizes are currently 8 and 16 GB, which explains why the Pro offers 16 or 32 GB, the Max 32 or 64, and the Ultra 64 or 128.]