The interesting aspect of watching a movie or TV show based on Marvel comics source material is that the viewer is usually just watching part of a story. In the case of Netflix's Daredevil, it is already planned to be a part of a bigger story as Matt Murdock will be joining a team known as The Defenders. There will be four shows that Netflix will air with these team members, and there are a lot of plans for Daredevil Season 2.
Business Insider reports that Marvel has a plan for its Netflix series from Netflix president Ted Sarandos. He says that "there will be a rhythm of about every six months you'll get a new season or a new series from the Defenders group". The Defenders is a plan to group the heroes from the Netflix Marvel Cinematic Universe together, which includes Daredevil, Jessica Jones, Luke Cage, and Iron Fist.
The Jessica Jones series will begin sometime in late 2015, and will star Kristyn Ritter and David Tennant. Then, six months later, there will be Luke Cage, which will star Mike Colter as the lead character. Another six months later will be Iron Fist, and I would imagine that the second season of Daredevil will have to fit in there somewhere, along with the Defenders series that will combine all four of these characters into one team.
We have mentioned in the past that Claire Temple is returning for the second season, who is the "Night Nurse" who mended Matt's wounds from Season 1. According to Yahoo News, one of showrunners, Steven S. DeKnight , mentioned that he wanted the Night Nurse to be Linda Carter, not the actress that played Wonder Woman, but a character from Marvel Comics. Apparently, Linda Carter is an important character in Doctor Strange's life, and so she will be appearing in the Doctor Strange movie. Like I said before, Marvel always has a bigger plan.
Another well-known Marvel character that will be appearing in Season 2 of Daredevil will be The Punisher. A separate announcement from Marvel states that Jon Bernthal, an actor best known for his roles on The Wolf of Wall Street, Fury, and TV's The Walking Dead, has been cast as The Punisher. For those who are unaware of this character, he is one of Marvel's most popular superheroes, but he definitely delves into some villain territory.
The Punisher has even had three movies made about him, and he is most famous for his shirt with the skull emblazed on his chest. It is not known if Netflix will use that look, but the Punisher, aka Frank Castle, was a war veteran with a family that was killed, and so he takes revenge on the criminals, by any means necessary. Yes, The Punisher kills his enemies, so I guess that makes him more of an antihero.
Is Castle going to set the storyline for Season 2? The Punisher has tried to kill the Kingpin several times in the comics. Sarandos has stated that perhaps The Punisher could get his own show, or maybe even a movie. "That's the beauty of it", referring to Marvel's Cinematic Universe.
Speaking of the Marvel Cinematic Universe, MoviePilot suggests that Daredevil, the character and possibly the actor, could somehow bleed into the plotline of Captain America: Civil War. The third Captain America film is going to debut on May 6, 2016, and it will be the first time that a major comic book crossover event has been brought to film. Daredevil had a part in that event in the comics, and considering that the Netflix Daredevil series does take place within the context of the Marvel cinematic universe (albeit a darker strain), this could easily happen. If nothing else, even a cameo of Charlie Cox as Daredevil would bring on the fan service.
Fan service could be the vision for Season 2. Marvel has recently announced that casting of Elodie Yung in the role of Elektra for Season 2 of the Netflix series, a very well-known character from the comic-book source material. Elektra was a fan-favorite character that Daredevil fell for, but was unfortunately killed by an assassin named Bullseye.
It is not known if Bullseye will be making an appearance on the show, as there hasn't been any casting information on this. The first season had allusions to these characters, but they were quite subtle. There is a scene where Matthew Murdock (Daredevil's real name) is talking with his friend and law partner Foggy Nelson, and the latter mentions that Matt had a girlfriend in the past.
There is also a scene in Season 1 where we see a sniper who happens to have a deck of cards near him. The sniper's face is not seen, but the cards could be a reference to Bullseye, who liked to employ them often.
Whatever the case, it doesn't look like Daredevil Season 2 will return to Netflix until sometime in 2016. There is the possibility of cross-overs with other shows that take place in this Netflix Marvel Cinematic Universe as well.