There was a unannounced change today with the anniversary - a change to egg distributions! Reports filtering through. 2nd gen starters return, Gligar and maybe others move from 10 km to 5 km, Houndour and Spinarak added to 5 km eggs, etc.
https://daily.pokecommunity.com/2017/07/07/new-egg-changes-ash-hat-pichu-in-pokemon-go/
https://www.reddit.com/r/TheSilphRoad/comments/6lqsq0/eggs_are_hatching_different_pokémon/
Pichu hatched from eggs obtained during the anniversary event (not before) also get a hat.
https://daily.pokecommunity.com/2017/07/07/new-egg-changes-ash-hat-pichu-in-pokemon-go/
https://www.reddit.com/r/TheSilphRoad/comments/6lqsq0/eggs_are_hatching_different_pokémon/
Pichu hatched from eggs obtained during the anniversary event (not before) also get a hat.