Sorry to hear that, @biophil. I had a good conversation with @andrarchy recently in the chat about the challenges facing Steemit regarding keeping developers informed of upcoming changes and of the API not being backward compatible and how serious of a problem that is. I think he has some good ideas he'll be working with them to implement.
See @proskynneo's reply which may be helpful to you. There are few things more frustrating for a developer than relying on a service or platform to build your app and then having it break to no fault of your own because of unexpected changes.
Please don't lose hope. I imagine HF19 may indeed have breaking changes (hence the need for a "hard" fork), but if they are communicated early and often, hopefully easy work arounds can be coded in long before it goes live. We all appreciate work you and everyone else does to build apps for the steemit ecosystem.