As we noted in our Gamescom 2015 coverage, Mafia 3 will take the series in a different (and, I think, more interesting) direction than the previous games. It will be set in late-60s New Orleans and set players off as a black Vietnam veteran named Lincoln Clay, who goes to work for the mob after returning from the war but is ultimately betrayed by the Mafia. Now it's time for some payback!
Steam says the game will be out in 2016, which as release dates go isn't the most useful bit of information I've ever run across. But an image from Best Buy posted on IGN, alongside Gamestop's online preorder link, give us a far more precise launch date of April 26.
The specificity of the date, and the fact that it's shared by two separate retailers, rather strongly suggests that it's legit. 2K declined to confirm it, however, saying only, “Mafia 3 will release in calendar 2016 during Take-Two Interactive's fiscal year 2017. No official release date has been announced at this time. It is common practice for retailers to list placeholder dates before an official release date has been announced due to the requirements of their operating systems."
That last bit is true, but those placeholders are most commonly the last day of the calendar year—as in this EB Games listing, for instance—and in case there was any question, April 26, 2016 does in fact fall within Take-Two's FY2017. We'll keep you posted.