Is there any other reasonable bet than HTML5?! Especially in the smartdevice realm where there is a rich set of HTML5-family features already enabled it makes less and less sense to make native applications except for special edge-cases. And any smartdevice competitors cannot possibly compete against iOS and Android on their own unique native app development format-- so HTML5 would seem the only reasonable place to focus development of new apps. Where Ubuntu succeeds is compatibility with an already well established Linux ecosystem.