I heard in their Q3 2023 quarterly earnings call that 6 years ago they left a PCIe slot free in every server so they could accommodate upgrades in the future as they grew. They were suspecting it'd be with the boom of AI/graphics cards but didn't want to commit to it yet.

Now they are plugging up that empty PCIe slot with newest gen graphics cards with their launch of Workers AI.

This is cool because they had foresight to make an uncomfortable decision initially but were able to respond to their growth objectives without spending capital expense to upgrade the entire servers.

Their recent blog on the design of the new servers is mostly around temperature, efficiency, and rack density. So unfortunately no hints at what's to come.