According to a short trailer released, it appears that the Marvel/Netflix Defenders series will drop on August 18th.  The trailer, which is called “Midland Circle Security Elevator B”, shows Matt Murdock (Daredevil), Luke Cage, Jessica Jones, and Danny Rand (Iron Fist) riding up in an elevator together.  The trick here is to read the timestamp which reads first ) 08:18, which to the savvy viewer would indicate the release date of the show as August 18th.  My guess is that we will find out quite soon.  You can view the trailer for yourself below: