An IGN article pointed out that the GameStop website has the PlayStation 3 and Xbox 360 versions of Mortal Kombat X listed as a June 2nd, 2015 release. This hasn't been officially confirmed yet, but it's possible that the last-gen versions of MKX could be released on that date. IGN said that they have reached out to Warner Bros. for a comment and will update their story as soon as they receive a response.
You can find the IGN article here:
http://www.ign.com/articles/2015/04/09/gamestop-lists-release-date-for-mortal-kombat-x-on-last-gen
If you missed the news, High Voltage (the devs who ported MK9, Injustice, and even MKX to PC) will be doing the last-gen ports of MKX. If MKX doesn't release on June 2nd on PS3/X360, we know that the game will be released some time in Summer 2015.