This is my thoughts on everyone coming back....
Mason is back to help Tyler get over being sired. He wants an apology from Damon, so that shows me that he really does want to help.
Lexie is back trying to help Stefan and bring him back from being a ripper. I love Lexie coming back!!!
Anna is kissing Jeremy (which I dislike emensly (sp)! Not sure if Vickie is going to be sticking around.
I think that when Bonnie helped get Vickie out of "the real world" something went haywire and the door was left open.
I think Grams may be a key to getting things back in order.
I hope they bring Jenna back to help Elana, Jeremy and most of all Alaric. They should bring back Rose as well for Damon. Anyway these are only my thoughts. What do you think?