I seriously doubt RAM will scale in such a linear fashion into the next generation of consoles.
First, it's safe to assume most if not all will stick with a unified memory architecture like the XBO and PS4.
System memory probably won't scale up considerably from current unless there is a greater dependence upon background functions running constantly. This would be useful for multi-tasking, but primarily for system functions and services as there isn't much benefit to running more than a couple apps simultaneously.
I would expect multitasking to be handled a bit more like mobile OS in that the OS would pause functions in certain applications as they are no longer being used, resulting in a minimal use of memory and suspended CPU functions.
So the question to ask is what resolution will the next generation of consoles be designed for? Presumably 4K as these displays become more common over the next 5 years. It seems doubtful any console manufacturer would support multiple displays as they simply aren't practical for the typical living room in which they are used.
At 4K resolutions, current video cards generally require 4GB of DDR5 dedicated to the GPU for current games. Back in 2008, when the PS3 and XB360 were running ports of PC games, the typical aftermarket PC video card had 512MB of dedicated VRAM with most systems set at 1920x1080. System memory was typically around 4GB, but this was rarely a restriction for game engines, even with the greater system memory overhead of Windows in gaming.
So the VRAM scale is already consistent with 4K gaming on PC, but consoles are hobbled by overall processing power by the CPU/GPU in the interest of cost, power consumption and size.
Of course consoles are typically designed to run games for the next 5 plus years, so it's not unrealistic to say that 9th gen consoles will be designed to run games being developed well into the mid, even late 2020s (!). Hard to project what sort of memory requirements games will have ten years from now.
Much of the memory allotments will have to do with the price of the memory being used in the late 201Xs when development on 9th gen consoles (hardware specs) begins to solidify.
I wouldn't be surprised to see anywhere from 16GB to 64GB unified, high speed memory being used, but I would actually expect a more conservative amount of memory if it accounts for 25% or more of the total BoM of a given console.







