FYI, it was proposed under BIP 151. Although it was withdrawn on 2019.
You already have end-to-end encryption: Start a Tor relay and add onlynet=tor to your bitcoin.conf. Now this will encrypt your connection without relying on a server-issued certificate, as there is no centralized server in this case.
I know we already can use Tor (or even I2P) to perform end-to-end encryption. But it's not part of rule which handle connection between nodes and not everyone would bother setup and use Tor/I2P.
As the comments section of BIP 151 says, an end-to-end encrypted P2P protocol won't actually stop surveillance (besides they can just use block explorers instead), or if somebody decided to make their blocks public, then any encrypted blocks and tx's sent to another node would be irrelevant as an interested party could just make the blocks available to someone else e.g. if a government agency runs a node then they can just inspect the data from the disk without involving the network.
JSON-RPC calls, however, are a different story. I would surely like Bitcoind to autogenerate a self-signed SSL certificate that is only used for HTTPS calls. If we can find a way to do this without OpenSSL, that would be great. I do not like the idea of passwords being sent unencrypted at all, and stunnel is too much of a PITA to set up - nobody will bother trying.