64GB is way too much. I can however see 32GB being a reality. With stacked RAM and lower power consumption with GDDR6/DDR4, it should be doable.. and wouldn't cost too much in 6+ years.
As for 4K? Nah. I doubt 4K will be mainstream anytime soon. With any hope, all that extra compute power should be able to better use like handle full working engines with real-time raytracing (much like Brigade). And estimating flops is pretty meaningless as well, because well , its impossible to tell how much AMD's GPU effiency will improve through their roadmaps.
@sethnintendo
DDR4 memory density has 2 times the density of DDR3. It's already in mass production from major RAM manufacturers (Micron Samsung, Hynix to follow). Having over 16GB of ram is not too far fetched for a 2020+ console.
Edit: typo
