According to Jason Blum, the producer of Insidious: The Red Door, the upcoming installment in the Insidious franchise may be the last one for a while. In the film, the Lambert family will once again face torment from demons, a decade after the events of the previous two movies. The focus of the movie will be on the characters Josh Lambert, played by Patrick Wilson, and Dalton Lambert, played by Ty Simpkins, both reprising their roles from the franchise.
During an interview with Discussing Film, Blum confirmed that there are currently no plans for any additional Insidious movies after Insidious: The Red Door. He hinted that if another movie is released in the future, it will not happen for a considerable amount of time. Below is Blum's full statement for reference.
Will The Red Door Really Be The End Of Insidious?
Get ready to witness the finale of Insidious - The Red Door! (laughs) However, in all seriousness, The Red Door marks the temporary end of the Insidious series. This doesn't necessarily mean it's the end forever, but rather a long hiatus. Who knows, maybe in ten years someone will come up with a brilliant idea, but for now, there is no concrete plan for a sixth Insidious movie, unlike its predecessors.Insidious: The Red Door is set to be the latest addition to the franchise following 2018's Insidious: The Last Key, which effectively connected all four films. Taking place long after the events of its predecessors, Insidious: The Red Door acts as a fitting conclusion to the entire series. Its significant emphasis on Dalton and Josh serves as a crucial element in concluding the storyline, as both characters fell victim to the Further in Insidious and Insidious: Chapter 2.
Blum's comments regarding Insidious: The Red Door as the current ending for the franchise suggest that he is specifically referring to the main series of films centered around the Lambert family and paranormal investigator Elise Rainier (played by Lin Shaye). However, there are already plans for a spinoff titled Thread: An Insidious Tale, featuring Mandy Moore and Kumail Nanjiani. This suggests that while Insidious: The Red Door may conclude the main franchise temporarily, there is potential for future films set within the same universe.
If a sequel to Insidious: The Red Door were to be made, it could potentially bring back an older Simpkins as Dalton. This idea for Insidious 6 has been hinted at by Wilson. This opens up the possibility of the future films in the Insidious franchise focusing on Dalton's experiences with the Further and how they evolve as he grows older. However, for now, it appears that Insidious: The Red Door will be putting this horror franchise on hold.
Source: Discussing Film