> I would happily pay $30 or whatever for each major update if it motivated the vendor to have an interest in keeping it up to date.

That would just be a different user-hostile incentive. The path forward is for Android to actually become consumer open source (GPL3). Let device manufacturers concentrate on shipping hardware and adding any new device drivers to a public repository. Updates can then be directly applied by eager users, or eventually pushed out by carriers with minimal integration effort. Proprietary "value adds" like SenseUI can still be done through the package system.