The interesting thing is that internet users adapt surprisingly quickly. This could play in to google plus. People on facebook already would switch in a second if all of their friends were on this new social network. And it isn't out of the question. It's an exponential curve of users over time. Sure, google might be playing too long of a long game, but it is certainly possible for them to take over social networking. If facebook becomes ad-central, google will be a surprisingly good alternative, considering they don't need all of their ads on google plus.

Personally, I don't use facebook or google plus right now. Neither of them have much benefit to me. Unfortunately, I might need to soon, considering a lot of people have the expectation that you should be using a social networking site. If you don't, you're an outcast, or have no friends. Sure, people like to boast that they don't need facebook to be social, but I hardly see this as possible in 20-30 years. In the very long game, social networks will become something that is just part of your identity, and if google plus keeps tabs on so many parts of your life, it could be the next big thing.