> There’s a 48GB B60 already

Kind of. It's more two 24gb b60s in a trenchcoat. It connects to one slot but it's two completely separate gpus and requires the board to support pcie bifurcation.

> and requires the board to support pcie bifurcation

And lanes. My board has two PCIe x16 slots fed by the CPU, but if I use both they'll only get x8 lanes each. Thus if I plugged two of these in there, I'd still only have two working GPUs, not four.