The Special Research quest bringing the second Mythical Pokemon Celebi is set to kick off next week, more precisely on 20 August 2018, so if you haven't had the chance to partake in the Chicago Go Fest event, Niantic have got you covered.
As usual, expect a bunch of XP-earning tasks, useful items and more. Being a Johto region Pokemon itself, Celebi's arrival will mark an uptake in the number of appearances by other Johto region Pokemon, so there will be no shortage of catchables.
In case you've taken part in Chicago GO Fest and already have Celebi, Niantic won't leave you hanging as the Special Research will still be available. However, completing the event will earn you a "new bounty of Candy to power up your Celebi."
In case you haven't finished up your Mew chores yet, you may not need to worry since you only need to have completed the third group of Mew's Special Research tasks to start the Celebi ones. In case you haven't done so already, there's still no need to worry because you've still got a few days to amend that.
If you consider yourself a Johto-region enthusiast, you should know that Niantic will be giving away a free Celebi T-Shirt for your avatar. I'm not sure of the ethical implications of hunting things with shirts of them on you, but I'm sure PETA's interests don't really include Pokemon protection.
On a related note, Niantic have announced a parental control platform for Pokemon GO called Niantic Kids, which should make managing your child's Pokemania a child's play. It will provide a parent portal via which you can review and set your preferred in-game permissions. Same goes for the personal information shared with Pokemon GO, which will also be controllable via Niantic Kids.
Also, as of today, 16 August 2018, Hoenn region legendary Pokemon Regirock will be taking up the mantle of Raid Battles from the steel-type legendary Pokemon Registeel. While it's defence is nothing to be laughed at, it is weak to water, grass, fighting, ground and steel type attacks.