What should those of us with existing 0.2.2 apps do?
Port at your earliest possible convenience. We obviously understand that might take a while and thus an EOL date has not been set yet for 0.2.2. It's officially in deprecated status, but likely will be quiet a while before it's removed completely.
In the future, all changes to the framework will strive to be backwards compatible and in the event it's not, we will have a clear EOL schedule. Unfortunately, those developing against 0.2.2 were on the bleeding alpha edge (as indicated by the version number) and thus some changes were inevitable based on the lessons learned. We obviously will do whatever we can to help those migrating to ease any pain points.