This makes me think of the not-so-recent deprecation of Offline Access by Facebook. I do not know whether it will be supported ad infinitum, but if not, it requires other completely-functional apps to be majorly rearchitected or break entirely.

There is rarely a good reason to actively destroy old API - section it off, keep it out of new code, maybe even kill the documentation so new developers don't use it, but it's bad business and downright disrespectful to the third-party developers who enrich your platform.