I don't see why Ubuntu couldn't start this in a small way, the way Google did with Android and T-Mobile. When the G1 came out, the word spread amongst us Linux geeks (because of the connection to the system) and to those who wanted some alternative to the iPhone. I don't think Google had any idea how Android was going to explode on the market.
So, why can't the Ubuntu folks find a manufacturer, maybe one struggling to keep up with the HTCs, Samsungs, Apples and other device makers, and build a prototype. Make it an unlocked GSM device, make it LTE capable, perhaps even multi-channel capable on HSPA+ so it works with T-Mo and AT&T in the US. T-Mobile is pushing their no-contract plans pretty hard, and a device that worked on their network might have some interest to some of their customers...it would certainly interest me.
Maybe I'm way off on this, but why not?