Daredevil season 2 just got it's first major casting announcement in the form of Jon Bernthal as the Punisher. This is the first solid piece of information on the season we've got. and from this we can speculate a lot about the next season of the Netflix exclusive. Spoilers ahead for season 1 and potentially season 2.
Kingpin Will Escape Prison Swiftly
Wilson Fisk ended season one of Daredevil in a prison cell. Most people assumed that he would escape at some point in season 2, possibly as a season 3 setup or for him to appear in the MCU Spiderman movie. The reason I think he will escape early in the season is because Punisher needs a reason to be in Hell's Kitchen. Punisher will either be hired by Kingpin to hunt Daredevil or, more likely, Frank Castle will see that Kingpin escapes and decide to go hunting where he meets Daredevil and develops a partnership to track down Kingpin. We don't know the specifics but we can assume Kingpin is the reason the Punisher is in New York.
There Will Be Less Hand / Chaste Than We Thought
The Hand and the Chaste are warring Ninja clans in the Marvel Universe. The Chaste (teased at the end of episode 7 and lead by Stick) and their war is what the internet thought would be the main plot behind season 2. The inclusion of the Punisher debunks this theory to an extent because the Punisher wouldn't pick a fight with ninjas. He's only really interested in fighting Mobsters and the like. It could be possible that they are featured prominently in the early episodes and take a back seat to Kingpin later on, or that Kingpin and the Hand develop some form of alliance (we know Kingpin will work with others to further himself), but both of these possibilities seem unlikely.
Will Bullseye Make An Appearance?
Bullseye is heavily rumored to be in this season (with Jason Statham said to be in talks for the role) but Punisher could stifle his inclusion. Theoretically, if Punisher is hired by Kingpin to kill Daredevil then he could act as a Bullseye replacement. Bullseye and Punisher are fairly similar in the role they could play to Kingpin if they went down that route. Perhaps Punisher gets hired, fails/switches sides and Bullseye becomes his replacement. It is completely possible that Bullseye could be later half and Punisher is in the early half to set him up for later appearances. Like all of these theories there are a lot of variables but it bring's Bullseye's role in question.
More Frank Millar Inspiration
In Frank Miller's Daredevil run (which season one was heavily inspired by) he used Punisher to contrast his style and attitude towards vigilante work to Daredevil. Season one already did this to an extent with Stick and Matt Murdock so it wouldn't be too far fetched to see them do a similar thing with Punisher. It's interesting to see them put so much faith in a writer that has destroyed his own reputation over the last 15 years.