There is no reason to transition… Literally keep what you already have. Ask yourself the following question:
Do I want to have a binary sensor based on a trigger or event? If yes, then use the new template integration.
It’s not a “new” format. It’s the format for the trigger templates. What everyone is referring to as “old” is not old. It’s the other type of template sensors and they are NOT going away.
They did not move. They are trigger templates not to be confused with binary_sensor and sensor templates. Please stop making it seem like it moved, you are confusing people.