Apparently, announcing that something is going to be announced is now a thing. 2K Games have confirmed that they will be announcing the existence of Mafia III with a trailer on 5 August. Which is weird, but okay (and at least it's not a trailer for a trailer, which is even more annoying).
Mafia III is, shockingly, the sequel to Mafia (2002) and Mafia II (2010), both developed by Illusion Softworks (now 2K Czech). Mafia was praised for its graphics - a massive step up from the then-contemporary Grand Theft Auto III and Vice City - and its highly memorable characters and storyline, as well as its measured pacing the clever way the city evolved between missions if long periods of time passed. Mafia II took place in a bigger city and of course was graphically more impressive, but its story was less compelling and its cast of characters altogether less memorable.
Mafia III has been developed primarily by Hanger 13, a new studio formed by veterans of LucasArts along with a couple of ex-Illusion staffmembers. 2K Czech is providing support, although a lot of the talent behind the first two games in the series have now left to form a new studio, Warhorse Studios, which is working on the medieval roleplaying game Deliverance: Kingdom Come.
Not much can be discerned about the game, but the cars and hairstyles in the only image released so far suggests that it will be set in the 1960s or 1970s. That makes sense given that the original game spanned much of the 1930s and the second was set in the early 1950s. It'll be interesting to see what Hanger 13 can come up with.