There's one fishy thing about Big Mam - why would she call herself that? Dragon for example doesn't call himself "Big Daddy". It would be only be if her identity is mainly consisted of her "motherness", like "when my daughter Lola was young, she said she thought pirates were cool and that she wanted me to be a strong one. I will do anything for my daughter, and here I am 35 years later, still hoping that she is proud of me".
Kaidou - well, there are no evidences for it or contrary. I wouldn't like it, as I want Kaidou to be an enemy (of course, Kaidou could still be an enemy since Franky's dad has shown to not be exactly good-hearted as he threw his son out).
Koala is 23, Nami is 20. That's downright creepy.
Luffy: We might see his mother. Oda already gave a description of her in case she is still alive.
Zoro: His parents could easily be some no-bodies. I don't think they are dead - just that Zoro left them on his own.
Nami: Her real parents are probably dead (warzone).
Usopp: Dad alive, mum dead.
Sanji: Probably non-important parents, even more so than Zoro. I guess they are probably alive (Sanji's days on Orbit could easily have been a short part of his education and he was supposed to go home afterwards).
Chopper: Depends on how old reindeer can become in One Piece if they are still alive. Were/are just common reindeer though.
Robin: I'd say that he has a fair chance of being mentioned again or appear. Just to know if he was from Ohara and if no, why would he get together with a wanted criminal from there?
Franky: Don't think they'll appear, but they have a bigger chance than Zoro and Sanji's parents, being confirmed pirates.
Brook: Probably dead, otherwise they would be 110-120 years old.