> But people who learn it for the first time will learn the new name, and official maps (etc) will all use the new name, and that's probably good enough.

Not necessarily. If the community isn't invested in the name change, the old name can remain current and persist through natural transmission.

In fact, the old name could become established as a way to separate the locals from tourists who learned a name from some outsider source like an official map.

Another factor is how good the new name is. "Mount Blue Sky" is actually pretty good, as far as these imposed renamings go. A lot of the time they're totally impractical mouthfuls (e.g. https://www.cbsnews.com/minnesota/news/federal-government-re...) that put contemporary English's orthographic sloppiness on full display.