Nokia Lumia 920 bought on eBay might accidentally be loaded with Windows Phone Blue
Similar to the way that notifications are handled on iOS and Android, multiple notifications are separated by app on the leaked Windows Phone notifications shade. There is also a revised multitasking section giving the user the ability to exit out of an app with a single tap from the multitasking view.
The UI on the phone also had a new weekly view on the calendar so that the user can make an appointment while looking at weekly information. And software can be called to the screen in order of "most used", "moderately used" and other headings. There is also a version of HERE Drive that mentions Beta BLUE. There are also a number of test apps designated by the letter "Z" which is something Nokia does with apps on developer units.
Is this all part of an upcoming update? There is some speculation that this is indeed part of the upcoming Windows Phone Blue update. Microsoft, for now, refuses to comment.
source: Reddit, TheVerge via SlashGear