It depends on how you think of "one machines". :) You can fit 1PB in 1U without something like NVMe-over-fabrics. So in a 4U unit gives you plenty of room.
We have Zen4c 128 Core with DDR5 now. We might get a 256 Core Zen6c with PCI-E 6.0 and DDR6 by 2026.
I really like these exercise of trying to shrink the amount of server needed, especially those on Web usage. And the mention of Mainframe. Which dont get enough credit for. I did something similar with Netflix 800Gbps's post. [1] Where they could serve every single user with less than 50 Racks by the end of this decade.
[1] https://news.ycombinator.com/item?id=33451430
