Blogger begin rolling out redesigned UI with a limited set of users who visit new feature testing ground, Blogger in Draft. At the start, only some lucky draws! can see the new design on Blogger in Draft.
Over the course of the next few days and weeks Blogger team will be ramping up to support all Draft users. There is no sign-up or activation process required from your side; just wait, and you'll notice your dashboard has changed to the new design when you log in to Blogger in Draft.
"Although our team has been hard at work cranking out tons of new features over the last year or so, it's been a while since our user interface has had a major update so we are very excited about Blogger's fresh new look. However, there is much more to the redesign than shiny new graphics and pages--we have essentially rewritten the entire application from scratch, using the latest web technologies that will enable us to make future updates in more agile and flexible ways," noted Blogger team.
[Source: Blogger in Draft blog]