Pokémon GO developer Niantic has confirmed that Gyms will be temporarily disabled starting Monday, June 19, in preparation for “some exciting new features.” During this period, any Pokémon you’ve assigned to Gyms will be returned to you. “As we get ready to update Pokémon GO, we want to ensure that Trainers have a sufficient heads up that Gyms will soon be disabled so that they can collect their Defender bonus,” explains a Niantic spokesperson. “We will provide updates on our social channels in advance of Gyms closing in-game.”
Source: @PokemonGoApp
Pokémon Blog 