Google says that Gmail will air over the coming months, and is "part of an effort by Google to offer all an experience that is more focused, supple and effortless." Users can also expect changes in Google Calendar, which will run over the next few days.
It is unclear whether the new Gmail interface will take over, but until then you can start using this trick:
The new Gmail has a cleaner, more refined look.
First, access Gmail and head to the mail settings. Then go to "Themes" and you will see two new songs, "Preview" and "Preview (dense)." Select one, and your inbox will immediately be adorned with a cleaner, more refined look.