I don’t see a lot of value in replacing TCP/UDP and further up the stack. But the value in replacing IP is having a permissionless way to join the network and not have a centralized address issuing authority. I also envision some sort of mesh wireless network as a permissionless physical layer to complement the permissionless addressing layer.
Discussion
Depending on scale, doesn't Zeroconf address this? I'd also have to look at a bunch of the mesh networks that are popular in the ham radio space to see what other protocols are in use.
In any case, I'd guess this is mostly a solved problem, but it's solved ABOVE the IP layer, not as a replacement.