That's the deal with backwards compatibility. Even third parties may depend on that name, it's not safe to go and change it.
On userspace that's the time when you deprecate an entire module and switch everything into a new name. The kernel does that once in a long while, but it's a bit harder for them.
The kernel doesn't care about third parties though, that's why the kernel API/ABI is not stable. This is one big advantage to doing it that way: sure, you need to have a consistent migration plan in flight to make sure you don't break mainline in the process, but you can immediately remove the old way without having to care about third parties, once you're done.
On userspace that's the time when you deprecate an entire module and switch everything into a new name. The kernel does that once in a long while, but it's a bit harder for them.