I'm sure it'll take a long time for Google to catch up, I just don't see most people moving to Google+.
Facebook has taught us a lot of lessons about having an online social life, but it appears to me that it hasn't learned much from us in return, other than what it wanted to learn. G+ feels to me like a second chance to get it right with better tools. To be honest, I would have no problem letting my facebook profile go stale, while I rebuild a better profile with G+. Something that prevented me from leaving facebook behind in the past was that there was no alternative. Now, I can gladly tell people "I'm outta here, if you wanna find me, I'm at G+", exactly like I did when I abandoned my hotmail account for gmail.
Anyway, I think Google+ will stay around and replace/fulfill communication needs for a lot of people but it won't beat Facebook. People LIKE seeing everything their friends post - even if they complain about it.