Any argument around "Email" should first define what email is. Does the author mean SMTP will last forever? MIME? IMAP? Email is a way of sending a message using a number of old, insecure and inefficient protocols. Will better alternatives to these protocols gain traction one day? Most definitely. What will remain of "Email" as we know it today is the addressing scheme IMO. The universally acceptable way of messaging a user@any-host is the real power of email, and will remain for the foreseeable future whilst transport and encoding protocols come and go (eg VoIP succeeding PSTN). In fact, email should last as long as the DNS system exists, given that the addressing system is directly tied to it. Being a flexible P2P messaging system, email can be easily extended to provide features of any "email-killer" app out there (including realtime communication) if need be. These innovations haven't happened simply because major email server providers dominate their existing markets (Exchange!) and have little incentive to innovate given the high barrier to entry for startups selling email servers to corporates. Email clients have seen more innovation, but there's only so much a client can do to extend capabilities of email.

plug: for this reason we're developing a full-stack email service in Node comprising client and server apps (end plug)