Blizzard has revealed when the servers will launch for Overwatch next week. In Australia, the servers will launch at 9:00am AEST on Tuesday the 24th of May. This is the exact same time that the beta launched a few weeks ago. Blizzard want to ensure that everybody is on an even playing field.
Blizzard have also detailed exactly how you can install the game ahead of time. You can read all about it HERE. Those who are purchasing on PC will have to download the Battle.net desktop app. You can already preload on Xbox One but there is no mention of preload happening on PS4.
Overwatch launches on Tuesday May 24th for PS4, Xbox One and PC.