According to recent job postings at Mafia developer Hangar 13, the studio intends to include stealth combat and may look into adding some sort of multiplayer mode to the game.

The details:

Reddit user ielboy1 discovered three new listings at Hangar 13 looking for designers to work on Mafia 4. The positions of Principal Designer AI and Lead AI Designer at the Brighton studio confirm that stealth combat will return from Mafia 3, with both roles tasked with "ensuring the delivery of engaging stealth and combat gameplay loops." Although the system was criticized by both players and critics for its lack of depth, it appears that the mechanic is being expanded upon further and may see more use throughout the game.
Until now, all Mafia games have been strictly single-player affairs, but the Senior System Designer listing has fans wondering if we'll see a new mode, whether PvP or co-op. The job description states that the studio prefers applicants to have "experience with AAA titles, multiplayer games, and/or live game design," which doesn't completely confirm its inclusion because it also mentions live game design, implying that the current trend of live-service elements could creep its way into the title. Some believe that a potential multiplayer mode will be nothing more than co-op missions that would be welcome as extra content, while others are concerned that Hangar 13 will try its hand at a Grand Theft Auto Online-style online mode, which has been criticized for its grind-heavy gameplay loop.
There isn't much known about Mafia 4 right now, except that it is most likely in pre-production as of March 2023 and will be built with Epic's Unreal Engine 5, replacing the third game's outdated Illusion Engine. Rumors have circulated that the plot will follow the Salleri family from the first Mafia game. The game will almost certainly be available on all current-generation platforms, but its release date is still years away, and Hangar 13 president Nick Baynes has stated that he plans to begin development on a sequel before the game is even released.

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Mafia 4 could include multiplayer elements and stealth combat