I've separated the movies from the TV and Online series. This should make it much easier to search for a specific movie that's under development.
My distinction between "Under Development" and the year by year pages (which I had previously labeled "Upcoming") is whether a release date has been assigned. When I first hear about a project (maybe when a work has been optioned) I'll log it here, along with any names associated with the project and maybe a reference to the original material. Once the project has been developed to a point where a release date has been assigned, I'll move it to the appropriate Movie [Year] page.
Although they may be ephemeral, the idea that these movies may happen is pretty exciting, and I'm happy to follow along as the ideas either evaporate or congeal.
ALIEN 5
Under development by 20th Century Fox
Neil Blomkamp directing
Not to be confused with Ridley Scott's Prometheus sequel, now titled Alien: Covenant (release date October 6, 2017)
ALITA: BATTLE ANGEL
Movie under development by Fox
From the manga series Battle Angel Alita (called Gunnm in Japan)
Avatar 3
Under development by 20th Century Fox
Avatar 4
Under development by 20th Century Fox
BLOODSHOT
Movie under development by Sony
Based on the Valiant Comic series
BLOODSHOT 2
Movie under development by Sony
Sony announced two movies base on the Valiant character
The Boys
Under development for Cinemax
From the comic series by Garth Ennis
The Bride of Frankenstein
Under development by Universal as part of their Shared Monster Universe
Deadpool Sequel (untitled)
Starring: Ryan Reynolds
Under development by Fox
Descender
Under development by Sony
Based on an Image series by Jeff Lemire and Dustin Nguyen
Dracula
Under development by Universal as part of their Shared Monster Universe
Dune
Director: Denis Villeneuve
Under development by Legendary Entertainment
From the novel by Frank Herbert
Dungeons & Dragons
Under development by Warner Brothers & Hasbro
GAMBIT
Starring: Channing Tatum
This movie was originally scheduled for an October 6, 2016 release, but was delayed indefinitely
Under development for Fox
Gotham City Sirens
Director: David Ayer
Starring: Margot Robbie
Under development
Based on the comic series by DC Comics
Green Hornet
Under development by Paramount Pictures
A re-imagining of the character as a gritty, updated version
HARBINGER
Movie under development by Sony
Based on the Valiant series
HARBINGER 2
Movie under development by Sony
Sony announced two movies based on the Valiant series
HARBINGER WARS
Movie under development by Sony
Harley Quinn Sequel
Under development by D.C and Warner Brothers
Hellboy
Remake is in the works
Independence Day 3
Under development by 20th Century Fox
Independence Day 4
Under development by 20th Century Fox
The Invisible Man
Under development by Universal as part of their Shared Monster Universe
Irredeemable
Movie under development by Fox
Based on the comic by Mark Waid
Knight Rider (Reboot)
Under development for the Machinima digital network
Lobo
Under development by Warner Brothers
Lumberjanes
Director: Emily Carmichael
Under development by 20th Century Fox
From the comic book
The Lunch Witch
Director: Clay Kaytis
Starring: Kate McKinnon
Under development by Amblin Partners
Based on the graphic novel by Deb Lucke
Mortal Engines
Under development by Peter Jackson
Based on the book series by Philip Reeve
The Prisoner
Remake of the 60's TV series
Ridley Scott to direct
Rampage
Starring: Dwayne Johnson
Loosely based on the 1980's video game
Rob Liefeld's Extreme Universe
Under development by Fundamental Films
Several films are being developed using characters from the comic series
SCOTT MCCLOUD'S THE SCULPTOR
Under development by Sony
THE SINISTER SIX
Originally scheduled for November of 2016, the status of this movie is unclear since the Spider-Man character is being relaunched.
Spawn
Under development by Todd McFarlane
Suicide Squad Sequel Untitled
Under development
Transformers 8
Under development by Paramount and Hasbro, as announced by Stephen Davis, executive VP at Hasbro, regarding plans for the Transformers franchise (see also Transformers 5 planned for release in June of 2017) through 2025. There are rumors of an animated prequel, a Bumblebee featured film, and a Cybertron prequel.
Van Helsing
Under development by Universal as part of their Shared Monster Universe
The Wolf Man
Under development by Universal as part of their Shared Monster Universe
Tomb Raider Reboot
Director: Roar Uthaug
Starring: Alicia Vikander
Under development for MGM and GK Films
Z
Under development by Lantica Media and Sobini Films
Directed by Jonas Cuaron
Based on Zorro but taking place in the near future