This is a complicated cost benefit analysis for Canonical. All of the device manufacturers with the exception of samsung are at the mercy of Qualcomm/Intel/Nvidia for the core drivers for their SOC. If a device manufacturer wants to experiment with an alternative OS, they are unlikely to make the commitments to the SoC manufacturers needed to get debugged drivers for a non-Android stack. By running of the Android Kernel and using Android graphics drivers, Cannonical has lowered the barrier to experimentation for device manufactuers. The cost of this is it complicated their developer story considerably. The reality of this is the developer story needs to be considerably fleshed out before we can judge it. All we know is that it will be different from the current Desktop Ubuntu story.