UPDATED (June 13, 2016 11:34 a.m.) - The Xbox One S will be available in August for $299. Xbox also announced Xbox Play Anywhere program, where all games purchased on the Xbox One will also be playable on PC, with some titles featuring cross-platform play.
The Xbox One Slim has shown up on NeoGAF!
Leaked a day before the the Xbox Press Conference, The Slim, touts a 2TB hard drive, support 4K video, and be 40% smaller than the original Xbox One.