I wonder how much this move was precipitated by Google's purchase of Motorola. Google produced each generation of nexus phone with a different manufacturer. This allows Google to learn the best practices of each of them. But eventually Google will produce the nexus devices themselves through their Motorola facilities, allowing them to iterate fast and produce cheaply. Apple sees this coming and figures out they also need to produce their devices in-house.
There's been 4 generations of Nexus phones with 3 manufacturers (HTC, 2x Samsung, LG). It seems like a bit of a leap to say that Google is learning the best practices of each and then will eventually use Motorola.
Not saying it can't or won't happen, just that you seem to be passing off your conjecture as something that's inevitable.
