Gazillion has confirmed that its free to play title Marvel Heroes Omega will be available for the Xbox One from June 30th. On the same day the PS4 version of Marvel Heroes Omega will leave open beta and become a full release, in line with the Xbox One version. Just last month the announcement was made that Marvel Heroes Omega would be released on June 20th, and a reason for the slight delay has not been shared.
It could be down to addressing issues found in the PS4 open beta needing fixes, with Gazillion wanting parity with the console launch dates to do so, Or something may have needed tweaking on the Xbox One version.
Source: Press Release