(Warning; this post contains logical thinking based on what is presented in the show. If you are a Prime fanboy who will ignore all facts in the show to have your Gods back, please do it peacefully and keep in mind, Prime and it's characters' story is over.)

Guys we're all idiots. Bumblebee and Ratchet have both made mention of being split up from Team Prime and not having contact with them for the longest time. Since Optimus was training in the Realm of the Primes for the longest time and hasn't been back on Cybertron since his return to Earth, it is safe to assume, the only Team Prime member besides Bumblebee he has had contact with since Prime, is Ratchet. Since Ratchet never had contact with any of the Team Prime members either, Optimus' group of old friends would probably only contain those off world he might now and Ratchet. Thus, they probably won't appear. Now just for sakes of confirming what left we have to deal with from Prime. To do this I'll list the status of all Transformers from Prime, dead or alive.
°Autobots
Optimus Prime - Investigating Cybertron's Government
Bumblebee - Bee Team Leader
Ratchet - Capturing war criminals with Undertone. Has contact with Optimus Prime after Decepticon Island.
Arcee - Unknown. Probably living her life. Won't return.
Bulkhead - Unknown. Probably living his life or working. He will return so I'll get to this later.
Wheeljack - Unknown. Probably living his life. Won't return.
Smokescreen - Unknown. Probably living his life. Won't return.
Ultra Magnus - Unknown. Probably living his life. Won't return.
Alpha Trion - Dead. Presumably in the Realm of the Primes.
Cliffjumper - Dead
Tailgate - Dead
°Decepticons
Megatron - Self exile. Might return.
Starscream - Captured by Bee Team. Won't return.
Soundwave - Captured by Bee Team. Won't return.
Laserbeak - Captured by Bee Team. Won't return.
Knock Out - Unknown. Probably living his life. Won't return.
Shockwave - Unknown. Probably living his life as opposing the Government or trying something evil would be illogical towards self preservation. Won't return.
Airachnid - Presumably dead on the moon.
Breakdown/Cylas - Dead.
Dreadwing - Dead
Skyquake - Dead in the Shadowzone.
Makeshift - Dead
Vehicons - Some were Prisoners on the Alchemor. Some probably scattered throughout Cybertron.
Insecticons - Many presumably dead on the moon, others like Razorhorn scattered around Cybertron.
Hardshell - Dead
Bombshock - Presumably dead.
Unicron - Trapped inside the Allspark Container
Nemesis Prime - In human captivity.
Predaking - Dead
Darksteel - Dead
Skylynx - Dead
As for humans, we don't know how long its been. They could be dead or the Bee Team won't contact them in order to hide from humans. Now as for why Bulkhead might return. He might be working as a Construction worker and met up with Ratchet or might be working off world and met OP. He might go to Earth for other reasons. As for the others who've been confirmed not to appear, Ratchet nor Bee have had contact with them. They're most likely living their lives and unaware of the council's actions or unwilling to start trouble. Probably the former. Megatron might return from exile and learn about the corruption.

 

So, if "Transformers Robots In Disguise 2015" is really believed to be a spinoff, since it's really acting as a sequel to "Transformers Prime", then does this mean there's really going to be an actual sequel to "Transformers Prime", with all of the cast members of "Transformers Prime" making their comeback to reprise their roles?

I'm so sorry about all of this, but I was only feeling curious about it.

 

Prime needs no sequel. It concluded all of its storylines and its characters have developed to their peak. Minus a few plot holes, which every show has, Prime is over. RID is about to go down the same route.

 

Great job on the list!Wow.

 

Thanks. Tried hard and went based on what Adam said.

On another note, Adam will no longer answer RID or Transformers related questions, possibly because he risked getting in trouble after speaking on which characters won't return or quite possibly due to the jerkish behavior from some "fans" trash talking him for not being their slave.

 

True...

 

BUT,one,Darksteel and Skylynx may be alive,you believe Starscream?And second,where did Predaking die?

 

According to Adam, before deleting all the Q&A stuff, said the comics aren't canon. He also said the Predacons are most likely dead.

 

I'm not talking about the comics.In Mighty Big Trouble,Starscream said to Bumblebee how he killed Skylynx and Darksteel.He didn't mention anything about Predaking.And most likely doesn't mean absolutely.Mr.Beechen says that to many questions that he doesn't have the answer to.

 

Also,Cliffjumper,Airachnid,and Skyquake are Terrorcons,not dead.

 

Wheeljack has became a punk criminal like Sideswipe,because Nightra mentioned a "speeding Wrecker".

 

He didn't mention any of them by name. He just said he killed the Predacons, the flashback only showed Skylynx and Darksteel. That doesn't mean, only they died.

Cliffjumper was killed after bevoming a Terrorcon. Terrorcons also need to suck Energon regularly, leading many to believe Skyquake died and Airachnif's death from lack of Energon was confirmed in a TFCC magazine issue, from what I've heard.

Everyone just assumes its Wheeljack out of desire for Prime references. Adam said it wasn't and Wheeljack wouldn't become that since he learned discipline and respect on Earth.

 

Interesting.

 

Was it ever made clear why the council wants Bumblebee?

I think it's because they want the great war forgotten. They exiled Ratchet, and sent Steeljaw and his team to bring Bumblebee back.

Maybe that's why Jazz hasn't returned. He said he will try and clear Bumblebee's name, right? The Council might've denied this and locked him away.

That's probably what happened to Team Prime. All but a few are locked away or even killed.

I know this is probably wrong, but it would be a cool idea to see.

 

They don't want the Great War forgotten, they hate the leaders of the original Autobot and Decepticon factions for having once destroyed Cybertron. So they split Team Prime up giving them distancing jobs and don't want Optimus on their world.

They hate Bumblebee for his unauthorized use of a Space Bridge to travel off world, taking a cadet and a delinquent with him. They probably want Grimlock and Fixit for not returning with the Alchemor and the rest of it's Caretaker Mini-Cons and Prisoners.

Jazz probably didn't return because he only came to investigate the message Fixit sent after the Alchemor crashed. Regardless if he could convince the Council or not, he still works for them and must do as they order.

 

I feel terrible for poor Bumblebee, especially all of the members of Team Prime.

 

Alright, cool. That makes more sense than whatever I said. Thanks!

 

Mr.Beechen said Jazz is not part of The Council.

 

He's not. He works for them as we saw when he came to Earth. Just as Ratchet works with them to capture war criminals.

 

OH,thx for clearing that up.