Upcoming Netflix series The Defenders will be 8 episodes

Thanks to We Got This Covered for the Marvel news.
"Marvel’s The Defenders’ follows Daredevil, Jessica Jones, Luke Cage and Iron Fist. A quartet of singular heroes with one common goal – to save New York City. This is the story of four solitary figures, burdened with their own personal challenges, who realize they just might be stronger when teamed together." - Marvel
The Defenders Confirmed To Be Eight-Part Series