As a former Pro DJ that now leads a Unified Communications Startup I find your comparison especially entertaining... and accurate. Vinyl records are still around now although they are more of a novelty item (no one is making real money on them). What has persisted is the analog user interface (especially around DJ'ing). While Email may persist in the future all your contacts and all your communications will be all together in one place. It is ABSURD that when we lose/misplace our physical phones we often simultaneously lose contacts and the ability to make/receive calls & SMS. It is also ridiculous that we can't all have a simple threaded chat log of our communications with all our friends/contacts regardless of if they were calls/SMS/Email etc. Different messaging channels are like different music genre's, many people used to think genre's like rock and hip hop were totally separate because the companies that marketed them worked hard to reinforce this distinction. As tools like the iPod gave the user more choice in how to organize and experience their music they blurred the lines between these genre's. The same thing will happen in messaging. People don't care whether it's a Twitter Message, Email, SMS or call. They just see it as all as communication and no one platform will win the day, it will be a mashup of all of them.