During the future of Arma livestream on Twitch, developer Bohemia Interactive has announced the 4th part of the series alongside Reforger as the next part. But this will probably be a long time coming.
Here's what's going on: On May 17, 2022 at 7:00 p.m., Bohemia Interactive started their live stream on Twitch and wanted to talk about the future of Arma. They have also done so and announced the official successor Arma 4 in addition to the next part, the Off spin Reforger.
However, there was only a teaser image to see for the Arma 4 announcement and the information that Arma 4 will only come when the enfusion engine is ready. Reforger should primarily serve to get more experience with the handling of the engine. But it may be a few more years before that happens. We also have incredible new details on Arma Reforger, which is already released by now: Arma Reforger Official: All Info from the Live Stream & Arma 4 Announcement