Roland Emmerich and Dean Devlin originally had plans to make a pair of Stargate film sequels, but their proposed movie trilogy never came to pass. Following their commercial success on 1992's Universal Soldier, Emmerich and Devlin decided to join forces on another original sci-fi film in the form of Stargate. The 1994 movie starred James Spader and Kurt Russell as an Egyptologist/linguist and U.S. Air Force Special Operations officer who travel across the universe using an ancient extraterrestrial ring-shaped device that creates a wormhole (leading to a similar device somewhere else in the cosmos).
Stargate went on to become a box office hit, setting a new October opening weekend record and paving the way for Emmerich and Devlin to make their alien invasion blockbuster Independence Day two years later. According to Devlin, he and Emmerich had always intended for the film to be the first entry in a trilogy, with each sequel focusing on a different mythology. However, MGM (which owned the Stargate rights) put the sequels on infinite hold in the wake of the franchise's success on the small screen, beginning with Stargate SG1 in 1997.
At San Diego Comic-Con 2006, Devlin revealed he was in talks with MGM to produce two Stargate sequels, with Spader and Russell potentially reprising their roles from the first movie. Ultimately, the negotiations didn't work out, though Devlin would continue to express his interest in making a Stargate trilogy on and off for the next eight years. Finally, in 2014, it was announced MGM and Warner Bros. were developing a Stargate reboot trilogy, with Emmerich directing and co-writing with Devlin.
Devlin later confirmed the Stargate movie reboot would actually be a remake of the 1994 film, rather than a legacy sequel or soft reboot featuring Spader and Russell in supporting roles. For better or worse, though, MGM's interest in the project faded after Emmerich and Devlin's Independence Day: Resurgence disappointed at the box office in 2016, suggesting the public wasn't exactly queuing for a revival of the pair's nineties sci-fi properties. A few months after Resurgence opened, Devlin announced the Stargate reboot had been put on indefinite hold.
The Stargate movie trilogy wasn't officially canceled until May 2018, when Devlin cut ties with both it and the Independence Day franchise. As the writer-producer explained, his experience on his directorial debut Geostorm (a sci-fi disaster thriller that had earned negative reviews and misfired at the box office the previous fall) led him to conclude he's "not the kind of guy who should ever work at studios". There hasn't been any talk of a new Stargate film since then, with Devlin and Emmerich spending their time and effort on different projects in the meantime. For all intents and purposes, the Stargate franchise appears to be finished on the big screen and is unlikely to make a comeback - not with Devlin and Emmerich calling the shots, anyway.