Technological changes happen like tides:  inexorable, imperceptible transitions from one state to another.  We don't realize the change until the water is "suddenly" three feet higher.

Note, for instance, the white-noise sound of static.   It is surely a 20th century phenomenon that most people born before 1980 will still recognize; but it has all but disappeared from our world, and will surely vanish from our collective unconscious in the next decade or so.   My children were all soothed to sleep to the sound of static - but by the time my son was born, it was hard to find a new radio that would play static.  All the new TVs and radios now filter out static, replacing it with silence (and in the case of TVs, a "no signal" message).  Without noticing it ever disappear, the sound of static is almost gone.

I predict email will go the same way.   It seems ludicrous now, but mark my words - in a decade or so, email will be as common as telnet.  Two closely linked pressures are killing it:  spam, and social media.   Spam drives us to be less than eager to give out our email accounts, but we still want to connect with real people - and that drives us to social media.   At the same time, social media provide a more connected experience than vanilla email.

The same is happening, at a slower pace, in business.  Large companies see the balooning size of the email server hard drives and put limits on mail sizes, and invest in collaboration sites.

The rub is that email is a free and open standard, and facebook et al. are not.  They are controlled by companies, both large and small, that may or may not have our best interests at heart.  Now, I do actually really like Facebook - but Facebook Inc. is motivated by the same thing every corporation is motivated by: money.  Well, I'm motivated by money too.  Yet this has lead to a very closely controlled ecosystem: there are no real competitors to facebook, twitter, and co because there is no sharing of data.  And there's the problem - no standard, no openesss, no opportunity for the organic growth that was the hallmark of the early internet - and email.

Anyway - most of us have not yet noticed, but the tide is sweeping in.  Like it or not, static is gone, and email will surely follow.