Kotaku is citing a pair of 'reliable sources' indicating that No Man's Sky will slip past its currently scheduled June 2016 release date and may not show up until late July or August at the earliest. According to a Gamestop employee, stores were informed that the date had changed since the printing of promotional material thus requiring the date to be covered up with "Coming Soon".
At this writing, no word has come from Hello Games about the delay so we'll keep you posted as the story develops.