A new Mafia game is in development at Hangar 13
Source and more: https://kotaku.com/mafia-4-release-date-hangar-13-haden-blackman-lucasarts-1848883555
Replacing Blackman is Nick Baynes, currently studio head at Hangar 13's Brighton, UK office, which Kotaku understands to be leading development on a new Mafia game. While the project is still early in development, its code name is Nero and it’s expected to be a prequel to the Mafia trilogy. The plan is to make it in Unreal Engine 5 instead of the Mafia III engine that was recently used for the remasters.
Source and more: https://kotaku.com/mafia-4-release-date-hangar-13-haden-blackman-lucasarts-1848883555