It should be noted that June 30th is a Thursday, and big releases often take place on Tuesdays. So this very well may be a place holder date. The expansion was announced last year by Blizzard, and a release in the month of September was also discussed as a possibility.
(Source)
The reason why the date was changed is unknown; however, it is important to note that the Warcraft film will release on June 10 in the US. It may be that the new date was set so Legion could ride the excitement of the live-action movie release as well.
Though only time will tell whether this rumor is true, the biggest takeaway is that WoW fans can look forward to a release during the Summer – ripe for vacation time.
