The main character of Mafia II, Vito Scaletta, was voice acted by Rick Paspualone, and it wouldn't be a longshot to think that he might be involved in the rumoured third installation of the series.
At least not after looking at some of his latest tweets. On two occasions he's dropped hints regarding a possible announcement, first when someone asked him for news, and later when someone asked about his Christmas vacation. Both times he mentioned Mafia.
The tweets are now being discussed on NeoGAF, and you can check them out for yourself here: