The end of 2012 is not too far away and Google+ certainly doesn't have enough momentum to dethrone Facebook in that amount of time. Some thing certainly will dethrone Facebook, especially with all of the privacy issues, but I doubt it will be Google+.
Google+ has a way to go before it becomes as ingrained in our consciousness as Facebook (or Google search engine) has become. At this point, it just doesn't seem to do anything that Facebook doesn't do, for better or for worse. I recently ran into a very interesting article based on an internal email at Google headquarters, one that basically announces that the Google+ experiment was a complete "failure." Might be too early to tell, but its interesting to see what the insiders are saying:
There seemed to be a lot of interest in Google+ when it was first announced, and many of my friends announced that they were leaving FB never to return. (I can certainly understand their frustration with FB, since I sometimes feel it myself.) However, most of them seem to be back on FB now. I get a sense that the air is leaking out of the Google+ balloon. However, I may be totally wrong about this. Only time will tell.
Like anything new, it may take awhile for something new to overtake the old, but l would imagine, it will happen -- probably not by 2012. Many years ago, I really liked by MySpace account, but Facebook is now my thing. I also suspect that if Facebook continues to make changes to the platform that irritate the users and limit or prescribe how things are done, then people will bail out to something new.
I've signed up for Google+, but there's so little activity on it that I forget it exists. I still use Facebook for almost all my social networking, and every other week I remember to log into G+, even though I use Gmail exclusively! The other posters are correct, it is a matter of time and waiting to see if Google will treat their users better than FB has in recent months... if Gmail is anything to go by, they will end up outshining the competition very soon!
I believe it will take more than a year for Google + to reach the incredible popularity of Facebook. Despite many complaints by Facebook users concerning the changes made on the site, FB only continues to grow in popularity. Ask this question again next year at this time, however, and the answer may be a different one.
That's really a matter of opinion. My guess would be that it will take more than a year for google + to gain the momentum of facebook. Right now, almost everyone has a facebook account while google + is still relatively new. Google does offer several great features that aren't on facebook. Facebook has attempted to make changes in order to compete with the circles that google + has, but many people are dissatisfied with these changes. In time, Google may come out on top, but I think that's going to take some time.