Sure; and everyone has a serial port, floppy disks and CRT monitors.

For anything to replace email, it will need to be decentralised. No company will trust facebook, twitter, google or anybody else with their private corporate data. It will also need to be obviously superior to email in almost every way. It needs to add features that people want.

The only serious contender for replacing email is Wave. I've been using it for the past 2-3 days and even as a beta I'm already preferring it over email. I'm honestly wishing everyone I need to talk to had a wave account already. Email will be around for at least 15 years. But I don't think it'll be around forever.

I could be wrong, but it would be prudent not to dismiss wave out of hand just yet.

To be fair, Wave is being developed as an open standard. Google is opening the protocol. They will also maintain an open source reference implementation for anyone to deploy in their own corner of the 'net.