It was previously reported that Google started launch new Gmail display for a number of users, at which time users can activate this new view manually via the settings page available on the Settings > Chat & Meet page > Make sure in the chat you have changed the option from Off / Classic Hangout to Google Chat.
But now it seems that this new look is ready to be released for all users, where slowly starting from today to the next 15 days, all users will be given a new, more integrated Gmail view.
With this change, users cannot revert to the old version, because Google has removed this option.
Then what has changed?, well for those of you who are not aware, now the Gmail interface offers better integration between Google Chat and Google Meet which users can access easily via sidebar on the left of the user’s screen.
Well besides that, you don’t need to switch to another tab if you switch to Google Chat and Google Meet, because both services will immediately open in the same window.
Via : Google