even though it would be optical, it still is using PCIe protocols in the background...

Hmm. What's the current maths on distance vs edge rate vs transceiver latency vs power consumption on when that would be a benefit? Not to mention how much of a pain it is to have good optical connectors.

I wouldn't expect that to be mainstream until after optical networking becomes more common, and for consumer hardware that's very rare (apart from their modem).