One of Kotaku's sources says Respawn's game is, surprise surprise, a multiplayer shooter, with battles featuring giant mechanical walkers called Titans - it was recently revealed Respawn trademarked the term 'Titan.'
Whatever it is, Respawn's game is under EA's co-publishing Partners program. Despite the label reportedly shuttering, the studio says everything's going "fine" for its next game. Presumably in response to Kotaku's story, the studio's official account tweeted "Wow! Lots of speculation tonight. Great to see excitement about our project but you'll all have to wait for E3 for details."
So... not May 21, then? Having said that, there's no denial there either. In any case, we've reached out to Respawn for comment.