You must be aware of the new Gmail Sign in page which is almost similar to the design of Google+. But now, Gmail as a whole has been redesigned (though not revealed yet). This news is not official, but it would have been so if Google had not made their official announcement on YouTube private. A video from Google channel explains the new look of Gmail but very soon they made it private, perhaps the Gmail team still has a few tricks left up its sleeve! However, you can find the video at the end of this post.
Some of the new features of Gmail include:
New Search box with Advanced search options being more prominent.