Whats Next?

So facebook is the largest social network. Almost everyone knows at least one person who has a facebook. It is a great tool. It has linked me back to numerous people that I never thought I would speak to again. It has even made me an awesome new friend from the other side of the world. People spend over 700 billion minutes a month on facebook. So my question is what will be the next social network to come out that takes over facebook? How much more can a social network do? Last but not least.... will it ever get big enough that everyone you yourself know will be a part of it? Let me know what you think.