2K announced Mafia Trilogy with an official trailer but retailers seem to have jumped the gun and revealed the release dates for Mafia and Mafia II Definitive Editions, with strong hints of a remake.
Mafia: Trilogy trailer, seen below, showed all three Mafia games with fancy graphics, meaning the older two got an overhaul. This is especially the case with the original Mafia, which was released in 2002, meaning were are likely in for a proper remake instead of just a remaster.
What the trailer did not reveal, however, is that the Mafia: Definitive Edition would release on August 28, which is information that came from Microsoft's store page initially. It has since been removed but the chances are that this is the correct date.
The reason for believing so is that it had screenshots packed in and the second leak coming from the store was regarding Mafia II: Definitive Edition which is supposedly coming on May 19. It is the same day that the description of the Trilogy video states new information will come along.
While the veteran fans of the series probably would have preferred the Definitive Edition of the original game to come along first, it is not the end of the world if Mafia II: DE releases first either. The main reason is because it is also chronologically the first game in the trilogy, followed by the original and finally the third entry in the series.
Further hints that the original's Definitive Edition is an actual remake also came from the MS store, which mentioned it was "faithfully recreated" while additional content and story was appended.