A post Email world?

Any time I see some pitch about a post-email world I immediately look to see what kind of walled-garden I'm being talked into. Because that's what they're doing.

Yes, email has been around 40+ years now.

Yes, it is based on some truly antiquated standards.

Yes, doing it right requires spending big money on spam filtering.

Yes, there is no inherent organization to email other than timeline.

And yet it still persists, no matter how many up and coming startups or well entrenched nigh-ubiquitous megacorps try and subvert it. It's still there. We all have at least one email address, probably a few. Why has email survived this long when so many other 40+ year old technologies have been dead so long they only show up in CompSci History of Computing courses?

• Email is simple, and helps people communicate.
• Email is extensible, which allows introducing things like filtering, file-transfer, organization, and collaboration, while still working the same way it always has.
  
• Email is platform independent, which means nearly anything can do it; the quintessential open standard.
• Email is everywhere, it's the one messaging system that nearly everyone has access to so people and companies can assume such a messaging conduit exists.
  

It's like talking about a paper-free office, you can cut down on the paper but actually getting rid of it will take a heck of a lot of work.

We may get to an SMTP-free existence at some point, but it's not likely to happen in the next 10 years.