Google released the demo version of the new Gmail back in April and gave the users an option to try the redesigned look. The response has been good for Google so far and the company is planning to roll out the full version in July.
Majority of the people have like the new User Interface (UI) which has made Google to go ahead with the full rollout. Once that rollout begins, users will still have the ability to revert back to the old Gmail interface for a period of time. Also, after 12 weeks following the rollout’s start, Google will force everyone to use the new UI whether they’ve opted-in or not.
You can find more details on the revamped Gmail here.