You guys are funny, but I don't want to take away your joy..
Bluebird is the symbol of rebirth, new beginning. Of course it has more meaning, but they are not going to use the most ridiculous meaning, but the most obvious one. That's why that Karl (producer) guy didn't want to say it..Because when we hear the title, it's obvious that Patrick Jane is going to have his happy ending. = bluebird.
He is finally going to let go of his past.
That's what bluebird means. When you list the other, more ridiculous meanings of bluebird, it's rather funny!:D As if the writers are thinking like that! They just look at the most obvious meaning, you should have learned that a long time ago, they don't think like we do!! Lol :))