Serebii has mentioned that Pokemon Quest is slated for release on June 28 on Android and iOS. The Twitter post is below.
Serebii Update: Pokémon Quest is currently set for release on mobile on June 28th 2018 https://t.co/gDbXkHSvkT
— Serebii.net (@SerebiiNet) June 20, 2018
Source: Serebii
