The official Pokémon website confirmed the in-game push notification that Deoxys Normal Forme will be available in upcoming EX Raids in Pokémon GO.

Deoxys Approaches in EX Raids!

Share an EX Raid Pass with a friend and try to catch Deoxys for the first time!

With Mewtwo appearing in Raid Battles for a limited time, it's time for a new challenger in EX Raids. Deoxys, a powerful Mythical Pokémon originally discovered in the Hoenn region, will be the next opponent in EX Raid Battles. This challenge begins with the next cycle of EX Raid invitations.

EX Raids will be more fun than ever thanks to some exciting improvements. When you receive an EX Raid Pass, it'll be easier to participate in EX Raids because you can now invite one of your Ultra Friends or Best Friends to go with you! By working together with your friends, it'll be easier to defeat Deoxys.

You need to win a Raid Battle at a qualifying Gym to become eligible to receive an EX Raid Pass, so working with your friends will also make it easier to get a pass. And now you can see which Gyms may host an EX Raid through a handy tag when you look at the Gym's details. Don't forget to battle at these Gyms if you'd like the chance to take on Deoxys!

Source: https://www.pokemon.com/us/pokemon-news/deoxys-approaches-in-ex-raids/