So once you have your phone, and your lengthy contract, there is no incentive for the vendor/carrier to perform an upgrade. They are technically delivering you your phone service with some "smart" features tacked on. All vendors are doing this, so there is churn at the end of contracts, but it will probably be a wash with everyone leaving their respective carrier for another one. Upgrades introduce regressions, and fixing those costs money, and that would eat into profits.
If the underlaying OS and the DE were split apart, or better yet, there was a firmware hooks to the radios that had standard calls from the OS, maybe there'd be a chance of some success here.(I'm thinking of how the original Xbox loaded the dashboard for XBMC) As long as you're tied to your vendors to provide your upgrades to you, you might as well be as closed source as anything that Microsoft puts out.
