With Supergirl coming to a close after six seasons, many are wondering if the end of the show also means the end of Kara Zor-El's adventures in the Arrowverse. Much of the concern is born from the fact that Kara doesn't have the best luck with endings in the comics and there is some feeling that the character, as part of the original Arrowverse founding Trinity, deserves a sizeable send-off equal to the one Oliver Queen got in the final episode of Arrow.
The decision to end the series at the close of Supergirl season 6 came in September 2020, shortly after star Melissa Benoist announced the birth of her first child. While not confirmed directly, it is suspected that Benoist wanted to devote herself to motherhood rather than try to balance the formative years of her first baby and the lead role of an action-drama. Whatever the cause, the announcement was made after a meeting between Benoist and Supergirl's showrunners, where it was agreed that season 6 would be the show's last. This has led to speculation that Kara Zor-El might die in the final episode of Supergirl, much like how Arrow ended with the death of Oliver Queen after he sacrificed himself to build a new multiverse in Crisis on Infinite Earths.
While Kara Zor-El deserves a suitable send-off, killing her off at this time may be anti-climactic. The show has teased Kara's death several times already, with a season 2 poster paying homage to the death of Supergirl in the original Crisis on Infinite Earths comic book series and Kara's death being hinted as a possible consequence of the 2018 Elseworlds event. Killing Kara now would lack the thematic impact of her sacrificing herself to save reality, as Oliver Queen did. Similarly, having her die to save Superman, as she did in the comics, would also be a bad look, given the character's long history of being subverted to make Superman look better.
Thankfully, there are several other options for ending Kara Zor-El's story without killing her. Ironically the best thing for the show might be to avoid a big showdown with Lex Luthor since it won't be possible to tie it into a major crossover event and season 6's opening will be based around such a battle already. Depending on Benoist's willingness and availability to return for guest appearances elsewhere in the Arrowverse, the easiest option might be an ending in the style of Justice League Unlimited, in which Lex Luthor and Darkseid were defeated, but there was a suggestion they would come back and that the Justice League would be ready when they did. Supergirl could easily arrange a similar ending that would leave National City's heroes free to cameo elsewhere, or move on to other series or spinoffs.
This seems far more likely than the theories that Kara would retire from heroism, given that nothing short of death could ever stop Kara from being Supergirl now. While some have predicted her settling down with a romantic interest (either migrating to the Kryptonian colony of Argo City, traveling to the future to join the Legion of Super Heroes or even running away with Lena Luthor), it wouldn't be in Kara's character to let others continue the Never-Ending Battle for Truth and Justice without her. It seems likely then that if Kara is not given a hero's death, she will continue to show up throughout the Arrowverse, whenever she is needed and whenever Melissa Benoist is free for a cameo.