I ran into this need today and put together a plugin that allows for selection of taxonomy fields and terms in the conditional rules.
Currently this is written only for ACF v5. I am unsure what it would take to also support v4 and if I plan to do that.
It should be as simple as install, activate, and start selecting taxonomy fields and terms as needed in your conditional fields.
Try it out and let me know if you run into any bugs! If it works well for others I will likely release this on the WordPress plugin repository (Unless Elliot wants to roll this functionality into core.
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