Niantic has announced the dates for the Pokémon GO Community Days from March to May 2022. Details of the featured Pokémon's were not revealed.

Save the dates: Next Season’s Community Day events!

Trainers,
Now that we’ve wrapped the final Community Day in the Season of Heritage, we’d like to share the Community Day dates for the next Season!

• Sunday, March 13, 2022
• Saturday, April 23, 2022
• Saturday, May 21, 2022

Stay tuned for the upcoming Season’s announcement blog for more details on March’s Community Day and more!

Please be aware of your surroundings and follow guidelines from local health authorities when playing Pokémon GO. Upcoming events are subject to change.

Source: https://pokemongolive.com/en/post/cd-savethedate-mar-may/