The concept of email is too fuzzy. Is it SMTP that will last forever? This technology is more like sending postcards that every middleman can read. Certainly a more private alternative will replace it someday, and it should be more spam-proof.

Also email serves many purposes. If it is to be replaced, it will be on a use-case by use-case manner. RSS is a better alternative to one-to-many mailing lists. Forums are a better alternative to many-to-many mailing lists. Etc.

But yes, we should improve what we have until we can replace it.