Marvell was recentlty showing off a a PCIe 6.0 Alaska-P retimer that's good for pcb, copper cable, & optical interconnect. Doesn't include optical transceivers but does show the growing interest in optical PCIe. https://www.servethehome.com/marvell-extending-pcie-gen6-rea...
Right now optical seems exotic & expensive but we seem near a severe tipping point. Copper keeps facing increasingly channeling signal integrity challenges, requiring expensive & energy consuming retimers. Meanwhile we think we can keep scaling optical down, integrating silicon photonics, getting increasingly lower pJ/b energy costs. Without the range & signal integrity issues. Not super duper deep but this 2 year old Cadence blog post goes into it, and it seems indeed to be where things are heading. https://community.cadence.com/cadence_blogs_8/b/breakfast-by...