In the comics, Elektra died and returned to life as a brainwashed assassin, then leader of The Hand; so, chances are that Daredevil’s several-time lover and ally will be on the side of the bad guys, led by Sigourney Weaver (!!!), rather than teaming up with Daredevil (Cox) , Luke Cage (Mike Colter), Jessica Jones (Krysten Ritter) and Iron Fist (Finn Jones).
Also announced, Jessica Henwick as Colleen Wing, who will first appear in Iron Fist, though was teased at the end of Luke Cage.