Microsoft is redesigning both the Azure AD and MSA sign-in pages so they have a consistent look and feel. I saw the new login today going to Outlook.com and embedded a screen shot of what I saw above.
The new design asks users for their username on the first screen and for their password on the second screen. Microsoft officials said in a blog post today that the two-screen sign-in provides "a notably higher success rate" using this approach and makes it easier to introduce new forms of authentication like phone sign-in and certificate-based authentication.
For those using Azure AD, users will see a banner giving them an option to opt-in to use the new experience. This is meant to give businesses time to verify their company branding, if used, works and to update their related documentation and training materials to reflect the new design.