I'm entirely convinced that Shuttleworth's vision of convergence will happen. It looks like an inevitability, as mobile computing power continues to grow faster than typical consumer workloads (the same forces already made it possible for $400 laptops to be good enough for most mainstream users).
Canonical just didn't have the resources to push a 3rd mobile platform. Hell, even Microsoft gave up (who did have the resources, and IMO made a mistake in giving up).