If you are worried whether or not to update because of reports that the update reset the progress of some players, there is no need to worry. The reports were based on underinformed social media posts by panicked trainers, who assumed they had lost their progress after launching the updated application. The issue affects only iOS users. Niantic has assured players that the update did not reset anyone’s progress.
The reason that the progress appears to have vanished, is because of the changes in the way the Google login is implemented in the game. Initially, users could sign in with any Google username and password. Now, this login mechanism has been changed and the Google login used on the iOS device in the Safari browser affects the login process of the game. This means that if users are logged into their work or alternative personal email ids via Safari, on the device, then Pokémon Go will use that email to login.
This caused a few users to login from a different gmail id without noticing it, and there immediate social media shares on their shock led to the story that the progress in some accounts were reset. To solve the problem, all one needs to do is to log out or switch to the email ID used to sign up for Pokémon Go in the Safari browser.