Why would HTC and Motorola follow the Nexus? What's in it for them?  As far as they were concerned the whole point of Android was that there <i>was</i> no reference implementation. 
If the start looking to the Nexus as a reference implementation all they get is to become box makers for Google's software.<p>As an Android developer, if you want to cover the whole market, you're now going to have to deal with handset makers at war with the developer of the platform. I can't see how the Nexus provides anything but more motivation for Android licensees to make their products significantly different from what Google is offering.