I don't think it can get the critical mass to pull people over from FB. FB is 20 times larger than Myspace ever was, and the reason FB took off was because it attracted more people than just teens, juggalos, awful bands, and gang members. Now that the void is filled and everyone who wants a social media hub is on it, it's pointless to add another one. It's 5 years too late.
I mean, how irritating would it be if Google+ actually got big enough to attract a decent amount of your friends, but many stayed on FB and never got Google+. I don't even like FB all that well to begin with, but it really does everything a social media site needs to do already, I damned sure don't want to have to get yet another social media account and screw with that. I don't even really care if it's better, because in FB I typically spend about 30 seconds a day at max on it. Check to see what messages/updates are there, click click done, log out.