In a recent interview K-Tai Watch (a Japanese news outlet), Niantic Japanese staff has revealed (via Translation) that the whole team is working on "a huge event for this summer", the next update will be a potential big change. It's possible that Niantic could be using a Big Event to promote and launch news "cooperative social gameplay experiences".
Today MmoGah.com would
like to share the good news that from Pokemon GO Hub
received a lot of reports via Twitter and e-mail that the mechanics of wild
Pokemon encounters have changed dramatically, most likely in preparation of the
release of Shiny Pokemon.
have reported that wild Pokemon no longer have the same core stats for every
player that encounters them. The following stats are unique for per player and
determined for his level on entering the encounter."
More details you can click this link: https://www.mmogah.com/de/news/pokemon-go/new-shiny-pokemon-and-more-pokestops-are-coming.