Keeping in touch with friends, family, and acquaintances is a core need for a large fraction of humans. Facebook, like everything, will disappear some day, but

Keeping in touch with friends, family, and acquaintances is a core need for a large fraction of humans. Facebook, like everything, will disappear some day, but it will be because people decide to start using some other way of keeping in touch -- not because they decide that they're bored of keeping in touch. Many people just stop using Facebook, don't replace it with anything else, and are happy with that decision -- but that will not be the norm.