Ubuntu focuses on mobile devices

It's a possibility, but it may happen that a part of the mass market that Apple is after will be pissed off as Apple gets more confident and tries to tighten it's grip on their pockets.
All those people, if this came to be, will be grateful that there's a door out of the walled garden: Ubuntu. I'm not sure if this is the plan of Shuttleworth. It's too quixotic and unpractical for his way of thinking, but it's really where Ubuntu is going right now: to became an scape way for a fraction of a fraction of the mass market.