why not offer direct access to mobile hardware and user information (e.g., mic, photos, contacts) through the device's native browser? they could mimic security restrictions of native apps and only permit access upon explicit approval (e.g., tap here to let site X access your camera and contacts). obviously, they can't wait for html5 standards, and would need to act on their own. but at least this would attract devs who want a web stack instead of forcing them to use the device's native language and the slower app approval process.
i'm not suggesting this will end apple's hegemony; it won't. devs will always build first for the platform where they can earn the highest ROI, which is usually the one with the most (profitable) users. yet minimizing barriers for devs to build, release, and test on a new platform would attract more devs and at least force apple's hand at maintaining web parity on ios devices.
are these companies afraid of undermining their own app stores? are mobile devices too slow still?
smart people run these companies. html5 is making some inroads, but there must be a reason why apple competitors are not pursuing this route more aggressively.