I really appreciate giving a 3 week heads up before moving to a new frontend structure. It's a nice gesture, but I have this horrible feeling that there's only about a 10% chance that my Hacker News app gets updated in time.
I know you can't not iterate because people are scraping, but it does stink. At least this will make everything more future-proof going forward.
However, it may be nice to give a bit more heads up than 3 weeks. I know a lot of apps can take ~2 weeks to get through the review process for iOS.