Not a brand new Mafia game, but a new edition of Mafia 2, which will obviously appear in a Definitive Edition, is currently being worked on at 2K Games.
This news comes from the Korean rating board, where the title for PS4 and Xbox One is listed. So, it seems that a remaster should be in the plans, since Mafia 2 was originally released for the previous generation of PS3 and Xbox360.
Mafia 2 told an epic story about the world of the mafia. With the 40s and 50s, the title spanned two of the most dazzling decades of the 20th century. Explore the city to the sound of Elvis Presley and Frank Sinatra with more than 120 originally licensed songs from the 40s and 50s and in over 50 classic vehicles of this era.
It is also not possible to determine with certainty whether it will only be a remaster – an enhancement of graphics in terms of higher resolution and/or better textures – or whether selected developers will add something extra. On the contrary, it can be expected with certainty that if the game actually comes out, it will include all the DLCs that expanded the story of the base game.
Why 2K is relaunching the game again raises some speculation. You may want to continue the original Mafia story in Mafia 4, which is rumored to be in the works. This would not be the first time that this entity reveals ports, games or remasters in advance, and when this happens, the official announcement does not arrive much later.