Consider the huge variety of messaging and discussion apps; it's relatively easy to embrace new communication tools.
EDIT: you might never silence SMTP altogether, but a suitable protocol could supplant it for the great majority of its use cases.
EDIT: you might never silence SMTP altogether, but a suitable protocol could supplant it for the great majority of its use cases.
The appearance of email being replaced exists in some places, but you find pretty quickly that you can't survive without it because it's still getting used for some critical communication or process.
The "new" email has been launched quite a few times now. It doesn't seem possible at this point unless all the major players agree on some new protocol which is seamlessly implemented in their mail services, while still allowing SMTP to function as a fallback to the improved protocol
I'm not aware of any alternative email protocol that's implemented, except TMTP. I don't believe closed-source, walled-garden services, which don't allow third-party clients or servers, really count as legitimate alternatives.
There's Matrix, but that's a synchronization protocol for chatrooms, not a store-and-forward messaging scheme.
https://en.wikipedia.org/wiki/Dark_Mail_Alliance
The stuff Ladar Levinson created after the Lavabit takedown, (famed for begin Snowden's email provider). Although I'm not just talking about email protocols; but additions or other improvements that always have the same problems (PGP encrypted email, or whatever Facebook tried to do when they reinvented email...)