Welll… let’s go through all the characters one by one:
Ryu - The main protagonist. Can’t die by default. Wlll however be on the verge of “defeat” and then plot armor kicks in and he beats Necalli
Explanation why he isn’t in 3S: Not needed, he was in SF3, 2I and 3S
Ken - Main protagonist’s friend, family man, been there since the beginning. Can’t die. Will help beat Bison or Necalli
Explanation why he isn’t in 3S: Not needed, he was in SF3, 2I and 3S
Chun-Li - Plot armor. Will avenge her father’s death, probably will help get Nash back to the good side
Explanation why she isn’t in 3S: Not needed, she was in 3S
Cammy - Plot armor. Will probably meet Decapre in a deadly fight. Will come out on top, but perhaps will have to sacrifice Decapre to save the rest of the Dolls. Then kick Bison’s ass and free them.
Explanation why she ins’t in 3S: Probably looks goes back to her Delta Red duty, gathers the Dolls in a safe place and looks after them
Guile - Will avenge what Bison did to Nash. Will be among the hero team in the final battle against Shadaloo’s boss
Explanation why he isn’t in 3S: Went back to the full Air Force service, not needed to enter SF tournament anymore, can live a happy family man life
Nash - The misunderstood anti-hero. Will use/help the hero team to defeat Bison. Will sacrifice himself to defeat Bison once and for all. Will finally have the proper burial he deserved since Alpha 2. Also will be revealed to Illuminati’s plans and maybe we’ll see Urien in action
Explanation why he isn’t in 3S: He’s fucking dead, that’s why
FANG - Bison’s right hand, 2nd in Shadaloo’s command. Will fight until the end to protect Bison at all costs, probably even if it means his own life, will meet Rashid in battle because Rashid will demand knowlegde about his friend’s whereabouts, also will disctract FANG from using his poison to stop the hero team from advancing. He will probably be completely crushed by Bison’s death and leave the base, don’t think the hero team will apprehend him.
Explanation why he isn’t in 3S: Works for Illuminati helping with their experiments after given an opportunity to do so by Urien or Gill
Bison - Will kick everybody’s ass, then suddenly Charlie comes in and they both die. RIP Shadaloo…or not? Ed will play a part in his story
Explanation why he isn’t in 3S: He’s in hiding, Shadaloo is destroyed, those who are still loyal to him might be scattered across the globe, but his new body won’t give him the opportunity to resurrect the organization and gather new forces. Probably disappears from the SF Universe once and for all
Rashid - Will be at first thought of as a villain, but revealed to be a good guy. Already friends with Ryu and Gouken, has contacts with Abel, Viper, Azam, Mika and Zangief, will help in Bison’s defeat. Hopefully will find his friend but he/she might be revealed to be already “gone”, sad plot twist
Explanation why he isn’t in 3S: Decides to travel the world in search for his/her friend, hoping one day they shall meet and find each other
Birdie - Former Shadaloo grunt, might give the hero team necessary information about the Shadaloo base. Might serve a higher purpose and help in defeating Bison or his forces, Karin might join him on the way
Explanation why he isn’t in 3S: Lives happily ever after at the Kanzuki Estate, faithfully serving Karin, forevers leaves his criminal past behind
Vega - One of the Shadaloo kings. Will betray Bison when his defeat will be obvious/at hand. Will use the SIN backup data for his own good. Probably will meet the hero team at the Shadaloo base and other locations, specifically for a yet another fight against Chun
Explanation why he isn’t in 3S: He’s rich as fuck and doesn’t need to do anything else. Probably gets rich by selling the SIN data to the highest bidder, whom might be the Illuminati. They will then use the Human Incubator program data to advance their experimentation and creating Twelve and begin his mass production, as seen in Twelve’s and Urien’s endings
Necalli - The main true antagonist and final boss of the game. Dies.
Explanation why he isn’t in 3S: He doesn’t exist anymore
Karin - Will hold a tournament. Tournament gets rekt by Bison and his plan, Karin is pissed. Goes with Birdie to the Shadaloo’s doorstep where she meets up with the hero team. They together kick ass. Fin
Explanation why she isn’t in 3S: Probably chillin’ at her Estate or entered the full scale measuring contenst against Ken’s business for the spot of richest company in the world, probably too busy with her own stuff and thus has no time for marrial arts
R. Mika & Zangief - both enter the tournament held by Karin as tag-team partners. At first they probably will help the heroes to defend the Metro City and then stay behind to beat up Shadaloo goons why the rest of the hero team goes at the Shadaloo base location to kick Bison’s ass
Explanation why they aren’t in 3S: Actively taking part in their respective wrestling leagues
Laura & Dhalsim - both stay away from the Karin tourmanent to protect the locals at their homeland. Dhalsim in India, Laura in Brazil. Also as seen in the trailer, both meet with the heroes at some point during the story, which means the hero team will investigate Shadaloo bases across the globe
Explanation why they aren’t in 3S: Laura opens up a Matsuda Jiu-Jitsu dojo/school, Dhalsim begins a full-time training program for teaching Yoga
Alex - Might follow FANG and Shadaloo on his own after the weird FANG experimentation to find out just what the heck did he find so special about Alex.
Explanation why he isn’t in 3S: Not needed, he was in SF3, 2I and 3S
Honorable mentions/possible cameos:
Balrog & Juri - obvious connections to Shadaloo. Balrog will as usually serve as a big brute and pucn everybody’s faces. Juri will most likely find her way into the Shadaloo base while everybody is busy fighting, as her intentions in this game seem to be aimed at her own goals rather than hurting somebody or something else since she’s not working with anybody directly this game
Ibuki - She and her ninja clan will play direct role in defeating Shadaloo as they join up forces with the hero team and invade the Shadaloo Base. Also she’s friends with Karin which means we might see her during the Tournament chapter. Especially if she’s released this month, which practically guarantees her appearance in the cinematic story
Sean - Might see Laura and Ken friendly sparring during the story which inspires Sean to study under Ken
Gouken & Oro - I think Gouken will introduce Ryu to Oro after the cinematic story so that Ryu might start walking down the path of an ultimate warrior achieving his full potential, essentially moving Ryu’s story into the New Generation arc
Helen - She might finally reveal her ture intentions and how she met up with/found Charlie, also there might be drop of info if she’s indeed an affiliate of Illuminati or working on her own
TL;DR
Bison, Nash, Necalli - will die
Guile and Ryu - might be severely hurt but still stay alive
FANG and Decapre - might be under the danger of death