I think Shuttleworth has just decided (probably correctly) that he can't make any money on the desktop, but mobile is still a possibility. The Unity interface and now this are an attempt to compete with Android.
I abandoned Ubuntu for my desktop when Unity came, but I think I might actually like it on a tablet or phone. Anyway, I'll try to keep an open mind when the devices actually come out. I hope one of non-Android Linux phone efforts finds a niche, whether it's Ubuntu, Jolla, Tizen, or Firefox OS. If Shuttleworth can pull it off, then more power to him.