I think it would still be a better approach than Google Play Edition phones, so it may survive to replace that concept. Meanwhile, the Nexus program continues to serve as the developer platform, with the marriage of hardware and software serving up what Google really wants to showcase and focus on moving forward. That leaves the Silver line to simply be good stock phones, with variable hardware left up to the manufacturers' whims.
That said - it's really anyone's guess what Google will do with these sales models.
I'm simply bummed that, if Motorola is finally under the Nexus umbrella, they appear to be starting at the wrong size. I don't want a 6" phablet, but I want a Motorola Nexus.
I love my Moto X, and not sure I'll be able to convince myself to get a new phone at full price before I've even had this one for a year. I am really curious to see what the next Moto X is like. Rumors are terrible following Motorola, because it's almost guaranteed they'll be releasing multiple sizes of their premium kit (probably same guts, different screen sizes and battery sizes) under the Verizon Droid brand... while they may only release one top-end worldly phone. I'm very curious to see how they approach it this year.