Hello,
Thanks for the feedback!
Yes this feature is planned, however it is substantially complex since it has to handle an unlimited of dependant fields (2/3/4/5… selects) and be compatibility with any kind of data (some users might want to use it for other data than country/region).
All these specifications make it really hard to implement in the current ACF UI. However, it should be possible, it will just take time. That’s why I don’t have any ETA yet.
Note that if you want to implement it by yourself in the meantime, I wrote a small proof of concept code using the ACF Post Object field, but you can adapt it with any ACF Select field. Here is the related support thread.
Hope it helps!
Have a nice day!
Regards.