[SPOILERS for those not caught up on Legends of Tomorrow ahead.]
The Waverider lost another one of its permanent crew members, as Jefferson "Jax" Jackson (Franz Drameh) departed Legends of Tomorrow in the show's winter midseason finale. Jax's future on the show has been up in the air for a few months now, ever since it was revealed that Victor Garber would be leaving Legends of Tomorrow partway through its ongoing third season. With half of the superhero team that is Firestorm stepping away, it begged the question: would Jax still remain aboard the Waverider, despite no longer having super-powers of his own, or would he be setting off on a new adventure without his fellow Legends?
Last week's four-part Arrowverse crossover, "Crisis on Earth-X", only raised more questions about Jax's future on Legends of Tomorrow, when it was revealed that The Flash's Cisco Ramon (Carlos Valdes) had devised a "cure" that would allow Jax and Martin Stein (Garber) to safely sever their psychic connection and, in turn, lose their super-abilities for good. However, tragedy then struck when Martin was fatally shot by one of the many Nazi footsoldiers from Earth-X and, upon realizing that Jax would eventually be killed too because of their psychic link, "Grey" drank said cure and allowed himself to die without taking Jax with him.
Jax then attempted to warn the younger Martin Stein (Graeme McComb) of his impending death in the Legends of Tomorrow midseason finale, 'Beebo the God of War', only for the latter to pull a Back to the Future and destroy the letter that Jax wrote him informing him of his death (except, unlike Doc Brown, young Stein didn't find a way to put the letter back together afterwards). Subsequently, Jax decided to leave the Waverider and its ragtag crew of superheroes and EW is now confirming that Franz Drameh will indeed no longer be a regular on the series, when Legends of Tomorrow returns in 2018.
Legends of Tomorrow showrunner and co-creator Phil Klemmer has likened every new season of the show to being a reboot, and so far that has resulted in major changes to the show's core cast every season, sometimes even within the season itself. Season 3 has already added one permanent member to the Waverider's crew in the form of Zari Tomaz (Tala Ashe) and may well have introduced two more in the midseason finale - namely, Leo aka. Citizen Cold aka. Earth-X's Leonard Snart (Wentworth Miller) and John Constantine (Matt Ryan), who made a last minute appearance ahead of his larger role in the Legends of Tomorrow 2018 midseason premiere.
EW is reporting that the door is open for Jax to return to Legends of Tomorrow in the future, though any and all future appearances by the other half of Firestorm would (arguably) not be necessary from a storytelling perspective. The Jax character has enjoyed the most dramatically impactful arc of any character on the show this season thus far, between him realizing that he can still lead an extraordinary life without super-powers (and away from the Waverider) and having to bid a final farewell to his father figure "Grey". If Jax does return to the Arrowverse in the future, it will presumably be to take part in a fun one-off adventure or two, seeing as his own overarching hero's journey has reached its conclusion for now.
As for the rest of the Legends, it remains to be seen if either Citizen Cold and/or Constantine will be continuously traveling with them through time and space now or serving as guest stars from hereon out. While the pair could make for a fun replacement for the old Firestorm team, there's a fair argument to be made that someone like Wally West/Kid Flash (Keiynan Lonsdale) from The Flash would be a more fitting choice to fill Jax's former spot in particular. On the other hand, The Flash might have big plans for Wally when the show returns next year, so it might be for the best that he stay exactly where he is and leave the time-traveling to others.
Legends of Tomorrow returns to The CW on a new night, Mondays at 9 pm, starting in February 2018.