My campus is working on upgrading our redunant 100gb ISP connections to 400gb next summer, so not necessarily just for HPC/AI/'massive datacenter'.
Granted,
A) our 100gb edge routers are reaching end of life
B) a LOT of grant proposals will be able to put down "400gb uplink on our campus", which helps land research money
C) The new routers will probably run for 5-6 years before we start scheduling an upgrade, so its considered money well spent on future proofing.
Our actual bandwidth utilization normally peaks at like 22gbps (every now and then we do see it get closer to 75gbps, but that's perfsonar running tests to/from other institutions).
Pdf warning: https://www.qwantz.com/fanart/superman.pdf
Superman actually controls the inertia of matter he comes in contact with.