This appears to be an entirely new category of Nokia phone if the naming convention applies. The Lumia 1020, Lumia 920 and Lumia 720 were all major releases suggesting this new "20" ended handset will be beginning its own class.
That supports the new 6-inch size which is expected to sport a 1080p display and, of course, Windows Phone 8. Nope, there's been no word of Windows Phone 8.1 sadly.
Other leaked specs include a 20-megapixel camera and Snapdragon quad-core CPU. The 1080p screen upgrade, known as GDR3, will mean an extra column of Live Tiles on your start screen, rotation locking, driving mode, and some minor UI modifications.
The phone is apparently being tested now with plans to launch, in the US at least, at the end of this year.