Not sure if it's "officially" confirmed or not, but there's not really any place for it to go with Jaye or Mal, unless you just want a super-extended Epilogue. Those aren't as interesting to read or write for many people, however. Stories thrive on character, narrative, and relationship development, and there's very little chance they'd invalidate any of the CS endings where Jaye and/or Mal ends up with the CS MC long-term for a "new" relationship with a different MC. That's how AVN devs get angry mobs with pitchforks screaming "NTR!"
The only reason they're including characters like Tara and Lisa in Firebreak is because there aren't endings in CS where the MC ends up with them long-term. Even those have had very polarized reactions.
They have said they plan to try to import the world state from CS into Firebreak though, so you might see cameos of Jaye or something, and might see your decisions and ending reflected there. She and Mal aren't likely to be a focus though, because all the other new characters need space.