> it seems like editing the prefs to update the file extension -> language mapping doesn't send any sort of event that would update already-open files. (@dangoor, is that true or did I miss something?)

Not directly. However, if you're editing the prefs file, you're probably *not* changing the mapping for `.json` files... so, when you switch back to the file in question, it should have the correct language. I just tested this by creating a `.foo` file and then switching to `.brackets.json` and mapping `foo: javascript`. Switching back to the `.foo` file, it was treated as JavaScript.