Outgoing top-down shooter Halo: Spartan Assault is set to be replaced by the Super Turbo Championship Edition of Drinkbox Studios' lovely metroidvania platformer, Guacamelee, as the Games with Gold offering on Xbox One in July (the other game that's available, Max: The Curse of Brotherhood, will remain available to download according to Microsoft).
On Xbox 360 there's a couple of new titles that'll be available for a free download next month. First up, on July 1, is shooter Gotham City Impostors. That game will be followed by the excellent Battleblock Theater, which will be available for free between July 16 and July 31. Just make sure your Gold subscription is up to date.