Language features either can, or cannot, be used.
Claiming that a language user should be prepared for certain parts of the language to disappear is a perfectly reasonable idea. But in practice it does not work. Because either it can or cannot be used, and if it can't be used it is a waste of time, if it can be used it must be supported.
Once people use a library, there will be pressure to support it forever and the mindshare switch is a real cost. A language bleeds users every time it drops a feature. The Python namespace is still polluted by documentation and tutorials talking about how to do things in v2 too.