The issue with shows based on comic book source material is that their book is happening while the show is being written, and comic book heroes never die, unless they come back to life. Last year, Netflix and Marvel took a chance with Daredevil, and it was a good bet. After that, other shows that took place in the same darker version of the Marvel Cinematic Universe began to show up, such as Jessica Jones, Luke Cage, Iron Fist, and also The Punisher. Right now, Season 3 of Daredevil and Season 2 of Jessica Jones are on the fence due to The Defenders, where all of these characters will be teaming up.
In the case of Daredevil, that comic book series has been going on for decades, there is a lot that can happen, but Daredevil actor Charlie Cox hopes at least one villain will appear. That villain is Bullseye, who was played by Colin Farrell in the not-well-received Daredevil 2003 movie. Cinema Blend reports that Jason Statham could have played hi, but that didn't happen.
Right now, the next season of Daredevil is really dependent on The Defenders. This goes for Jessica Jones Season 2 because it is difficult for all of these characters being brought together and then set them apart again.
Marvel's Netflix shows have started an interesting pattern of tying themselves together. While Daredevil Season 1 was made to stand alone, Jessica Jones went ahead and introduced Luke Cage (Mike Colter) right away. Luke Cage will have his show on Netflix beginning on September 30, and it looks like his adventures will take place in Harlem and not Hell's Kitchen. It is possible that some seeds for the next show, Iron Fist, will be similarly planted.
Iron Fist is, after all, the partner of Luke Cage for several years in the comics. His powers are mystically based, and many believe that Madame Gao, who is making a drug known as Steel Serpent in Season 1 of Daredevil, could be tied in to Iron Fist's series. Season 2 of Daredevil featured the ninja action from The Hand, and the mysticism (including a foe that was raised from the dead) seemed out-of-place on Daredevil, which shouldn't really delve deep into the supernatural.
It is possible to sew these shows together. At the end of Season 2 of Daredevil, Foggy Nelson (Elden Henson) worked for Jeri Hogarth (Carrie-Anne Moss), who is an ally of Jessica Jones (Krysten Ritter). This could allow Foggy to get to know Jessica, and then Jessica can get to know Daredevil. Pairing those two will be the beginning. Then Jessica, who knows Luke Cage, can introduce Daredevil to Luke. Maybe by the time the Luke Cage and Iron Fist shows are aired, those two characters will all know each other.
The issue is why will these characters be brought together? There is the villainous Wilson Fisk (Vincent D'Onofrio) who seems to want revenge on Matt Murdock (Daredevil's real name), but Jessica Jones' greatest enemy of Kilgrave (David Tennant) is dead. Luke Cage is going to have a few enemies on his show, and as for Iron Fist, very little is known about his show.
So, is there going to be a group of villains that will band together to defeat these heroes? It could be, as there is some kind of master plan showing up on Daredevil. I don't see why not, but is this group going to be The Defenders, and have their own solo shows?