A day without a Nexus rumor is like a day without sunshine
There's been a rash of rumors the past few days about an unannounced 5.9-inch phone from Motorola (see Android Police and The Information for their excellent coverage of all of this), and most of them say that this device will be the Nexus 6. What you've probably heard is that the Motorola Shamu, based on an entry in Google's bug-tracker system, is the next Nexus, and ready to take on the also unannounced iPhone 6, and we will see it shortly after the Apple announcement.
Like most rumors, this is surely based on some sort of proof, but a lot of it just doesn't make sense and we're not yet ready to declare anything as the next Nexus.