They confirmed that the second season will last for nine episodes, even going as far as to announce the episode titles in the preview video. Those episode titles are:
- The Boy Who Came Back to Life
- The Pumpkin Patch
- The Palace
- The Storm
- The Pollywog
- The Secret Cabin
- The Brain
- The Lost Brother
The Duffer Brothers have already been working on and planning the second season for a while. They've started submitting the scripts to Netflix and are looking to cast four major new characters for Season 2. However, they've confirmed that most of the major Season 1 characters will return but would not be drawn on if Eleven will be back, which given the ending of Season 1 is understandable.
To avoid the curse of bad sequels, the Duffer Brothers have apparently been studying the works of James Cameron, judging Aliens and Terminator 2: Judgement Day to be the finest sequels ever made. Hopefully something rubs off and the second season of Stranger Things is as good as the first, if not better.
Season 2 of Stranger Things - and apparently there's a good chance it will be called Stranger Things II - is expected to air in late 2017.