According to MP1st, a new Just Cause game was in development at Sumo Digital.
The information comes from the profile of a former Sumo Digital employee, who worked as Lead Vehicle Artist on the project from 2021 to 2023 before it was ultimately cancelled.
The mention of Sumo Digital is particularly intriguing, as Avalanche Studios has traditionally been the primary developer of all mainline entries in the series thus far. This could suggest that Square Enix, as the intellectual property owner, chose to outsource development to Sumo Digital. Alternatively, it may simply indicate that Sumo Digital was collaborating with Avalanche or another studio on the project.
However, given that Avalanche has been focusing development on the cooperative title Contraband since 2021, their involvement in this new series entry seems unlikely—though this remains purely speculative.
Despite reportedly having no game in development, a Just Cause film is in production.