Rumor has it (and this rumor makes so much sense I'd go as far as to say Google would be absolutely insane not to do this - hence why I personally believe the rumor is true, but you should choose to believe it at your own discretion) that Google is going to, with the next major revision of the Android OS (called Froyo), start a different approach to updating. Who knows if they'll consider this "2.2" or "3.0" or "2.5" or whatever.
The rumor says Google is going to stop working so much on the core functionality of Android and instead move to better developing apps (GMail, Calendar, Phone app, etc.) and release these apps through the Android Market.
[Hypothetical] For example: Google will update the calendar application to have a better reminder system, and do other things well, and add some new features, maybe a better widget with more size options, etc. They will release this update via the Android Marketplace and then anyone who has the appropriate underlying OS version will be able to download the update (for example: maybe the update is limited to those running Android 2.0+).
This is a much better system that, while leaving in place a small amount of fragmentation potential, reduces the need for so many OTA updates and worries about many phones not getting certain updates. This way, more people get everything, and less people get nothing. It's overall a better system and makes a lot of sense to me.
