nip-4 and nip-44 are current standard of quality of encryption with ecdh and AES based cryptography i think it could be made a lot stronger, of course, especially if we start to talk about adding synchronous handshake protocols for DMs (i mean, if someone is currently live in chat, why not?) but we only just finally got broad support for auth which was a prerequisite for anything further involving mediated private communications... i wouldn't be holding my breath on the question of actually decent functionality but the possibility is there and it only takes the partnership of a competent relay and client dev to become a reality