Leaked by way of an advert
[Update: it’s been officially confirmed by Blizzard.]
Over on reddit, an astute reader of IGN found an ad campaign for Overwatch that happened to be emblazoned with the release date — May 24. Before then we didn’t have an exact date from Blizzard, and the campaign presumably was switched on earlier than intended.
The game is currently in a closed beta, and will hit the PC, PS4, Xbox One platforms. They will not feature Cross-Play. The open beta will also reportedly go live on May 3.
Found Overwatch release date! [reddit]