This could potentially be great news - I've been working on an Uber client app for Firefox OS [1] using the reverse-engineering done by the Uber CLI project [2].
It's pretty a pretty basic implementation at the moment (you can currently book a ride based on an address, and not much else), but allowed me to move to FirefoxOS for my primary phone - Uber being the last 'must-have' app for me that didn't have a webapp version.
Having something official to work with (assuming they don't go down the Twitter route of not allowing anything that replicates the functionality of the main Uber app) would help a lot.