Supergirl will take down Project Cadmus by the end of the season -- but Lena Luthor (Katie McGrath) will be sticking around.
McGrath has been promoted to series regular for the show's third season, according to Deadline, which means that no matter what happens with Lena's mother -- who is running the evil anti-alien group tormenting Kara (Melissa Benoist) and her friends -- Lena will be sticking around. She first appeared in Episode 4 of the sophomore season and has made appearances in a total of seven episodes so far.
The last time we saw Lena Luthor she was playing a game with herself after an episode of playing both sides of the fence between Kara and Cadmus. The closing scene showed that there's a lot more to Lena Luthor that we don't know, but are anxious to see. McGrath's promotion proves that Lena's chess match will probably be more of a long game and there's much more the producers would like to explore with the enigmatic character.
On the show, Lena Luthor is the younger sister of Superman's great foe, Lex Luthor. Since Lex has been sent to prison, Lena has taken over Luthor Corp. and is trying to rehab her family's image. That's not so easy when her mother is also a die-hard anti-alien zealot, but it seems that Lena is controlling all of the pieces on the board here.
Outside of the politics, bumping Lena up to series regular means more time to build the friendship (or adversarial rivalry) between Kara and Lena. The two have become professionally and personally very close over the tenure of Lena's stint on the show. Since Kara is currently unemployed, it's very likely that Lena could be the source of Kara's next professional endeavor. But most importantly, it means the characters' growing legion of 'shippers can get even more excited.
Supergirl Season 2 continues Mondays at 8/7c on The CW.