I think the open web-applied to smartphones-will be what the entire smartphone market eventually arrives at. Mozilla is playing the long game and doing a lot of extra work and will go through a lot of issues that they wouldn't if they made another walled garden OS and marketplace. One of the reasons that the web is so popular for developing apps is its openness and prevalence. The more momentum firefox OS builds, the more pressure will be put on other phone OS ecosystems to follow suit, especially if you can use firefox within other ecosystems and it integrates well with their marketplace and apis. When that happens, it will be increasingly hard to justify creating a device specific app when you can cover every device with one webapp.

This will be an exciting project to watch.