Square Enix submitted a business report to its investors about twenty days ago, and as part of it, it somehow missed the information that they are developing a new game from the Just Cause series. This has now been noticed by one user of Resetera in the transcript of the meeting with investors, so here it is - there will be a new Just Cuse, which confirms the suspicions that you may have had.
Just Cause is one of the "western" series that Square Enix did not sell, which was already an indication that they see a future for it. The last Just Cause (4) came out at the end of 2018 and was not particularly famous - it was the worst-rated game in the series. There has been talking for years about a film adaptation of the series, but nothing has materialized on that issue yet.
The game's developers, Avalanche Studios, are currently developing one well-known game - Contraband Smuggling Simulation, for PC and Xbox Series X / S. It was also rumored that they may be working on a sequel to Mad Max.