here is my prediction for the new Nexus 4.
Made by Motorola with the Nexus 4 design look at front, Moto X back and edge to edge display.
Now about update, here is what Motorola did with the OS after Google bought them.
Removed most Motorola applications and replaced it with Google apps.
replaced My Gallery,Alarm & Timer and My Music with standard Google applications(Android).
Chrome is the new browser on Moto X. Keyboard i believe is Google Keyboard
Also they ripped the features that was integrated in to OS and made it as an app. even better they published it to Playstore so that they can update without OS update.
what does this tell you?? there is less app for Moto to build/Test to get the update pushed.
Most build in app is now handled by Google and that saves them time. Moto dont have to worry about those apps at all.
Since many features are ripped to apk less work merging code of new version of Android.
Moto X wont get update like the Nexus 4 but it will be faster than other OEM.