Marvel and Netflix have two shows going on next year (Daredevil Season 2 and Luke Cage), which seems to be the maximum they're willing to go per year right now. I'm assuming they can't stretch their overall budget, time, and manpower out to work on three shows simultaneously.
Maybe we'll see Jessica Jones Season 2 and Iron Fist Season 1 in 2017.
Edit: I looked into how long filming took for both Daredevil and Jessica Jones, and either Wikipedia is messing with me, or Daredevil really only took around three months (October to mid-December 2014) and Jessica Jones took around seven months (February to mid/late-August 2014). Not including post-production, which probably pads on even more time.
Maybe we'll see Jessica Jones Season 2 and Iron Fist Season 1 in 2017.
Edit: I looked into how long filming took for both Daredevil and Jessica Jones, and either Wikipedia is messing with me, or Daredevil really only took around three months (October to mid-December 2014) and Jessica Jones took around seven months (February to mid/late-August 2014). Not including post-production, which probably pads on even more time.