There are semi-compatible ways. My favourite proposal (if we couldn't have IPv6) was recursive IP: you transmit a packet to 12.34.56.78 and inside that packet is a packet addressed to 192.168.1.5. If you have more layers of NAT, inside that can be a packet addressed to 10.1.2.3.
If both endpoints do this you can directly establish connections. If only one does it, fall back to NAT like before. Core internet routers don't have to be updated. Addresses at endpoints are effectively variable-length.
If both endpoints do this you can directly establish connections. If only one does it, fall back to NAT like before. Core internet routers don't have to be updated. Addresses at endpoints are effectively variable-length.