So this is a list of who I think will and will not return. I will TRY not to bring my opinion into this, but I might slip up a little. So, let's start this list!
Okay, so the characters I don't think will return are:
Leonard, Beardo, Blainley, Rodney, B, Justin, Staci, Beth, Eva, Scarlett, Topher, Max, Dakota, Ezekiel, Geoff, Lightning, Jo, Sam, Cameron, Mike, Zoey.
So I'll explain some of these characters and why I don't think they will return, or at least yet.
So Leonard, Beardo, B, Eva, Rodney, and Staci first. These are all characters that I believe their purpose was to fill a spot to get out early on. With barely enough development (I know that characters like Beth, Noah, and Cody got developed, but these guys seriously cannot get much added on.), there isn't really anyone that is a fan of them, so putting them in the next season wouldn't be a smart choice. However, if any are added, Eva will definitely be added, because she has the biggest fanbase, and I am a fan of B, so I would like him, but it's unlikely.
Blainley, Justin, Beth, Scarlett, Topher, Max, Dakota, Ezekiel, Geoff, Lightning, Jo, Sam', Cameron, Mike, Zoey'.
Ezekiel and Dakota are quite obvious, as they are mutants, so adding them in the new season would make no sense in any way at all.
Blainley, Justin, Beth, Scarlett, Topher, Max, Geoff, Lightning, Jo, Sam', Cameron, Mike, Zoey'.
Blainley was a slap in the face character, just to steal the spot of Beth from returning in TDWT. She was unlikeable and just didn't seem fit for TD, only competing in 2-3 episodes.
Justin, Beth, Scarlett, Topher, Max, Geoff, Lightning, Jo, Sam', Cameron, Mike, Zoey'.
Justin got more than enough screentime in TDA, and he just wasn't that good of a character anyways.
Beth, Scarlett, Topher, Max, Geoff, Lightning, Jo, Sam', Cameron, Mike, Zoey'.
Beth and Geoff were two winners that were winners for no reason. Beth was just carried, and she was definetly not a fan-favorite, and same with Geoff and the Surfer Dudes. They both recieved way too much screentime and hopefully won't be returning soon.
Scarlett, Topher, Max, Lightning, Jo, Sam', Cameron, Mike, Zoey'.
Scarlett, Topher, and Max were all good characters, in the better half of PI, but since they were all kicked off by Chris, a return is probably unlikely, although Chris CAN bring them back with their contracts, but since HE kicked them off (or tricked Topher out), he probably doesn't want them back.
Lightning, Jo, Sam', Cameron, Mike, Zoey'.
Cameron, Mike, and Zoey were too featured in AS, so everyone is sick of them and doesn't want them to return soon.
Lightning, Jo, Sam.
I believe that Lightning, Jo, and Sam all failed in AS and aren't likely to return, but they will probably return in a later season.
Now on to the characters I think will return.
Duncan, Bridgette, Leshawna, Harold, Noah, Cody, Shawn, Sky, Dawn, Scott, Alejandro, Lindsay, Brick, Sugar, Dave, Courtney.
I don't really want to explain why I think they will return, but most likely because they are either fan favs, staples in the series, or just better developed then the others.