Case in point: in the 1990s, portals were big, and every popular website wanted to be a portal. Likewise, between 2006 and now, most popular websites integrate social features.

What people seek in Facebook, they'll start finding in more directed services. Facebook was made for a world where smartphones and affordable or free fast mobile internet access was rare. A shrunk version of the regular web version can be enough for adults who are already used to Facebook, but teenagers and children will flock to user experiences that explore the advantages and idiosyncrasies of smartphones.

Maybe Facebook the company will own some of these new services and interface ideas, but Facebook the old timeline/friends/profile service will get obscured by the new, shiny, more intimate new services.