Google Announced Android M's name and it's:
M is for "Marshmallow"
Also See Galaxy Note 5 annunced:
Android M includes a simpler approach to permissions (while giving users more granular control over what apps can access), Google’s new Android Pay mobile wallet platform, USB Type-C support, and a number of tweaks and improvements throughout the operating system. It succeeds Android 5.0 Lollipop, which brought significant user interface and visual changes to the software last year.
Also See S6 Edge +: