This would be extremely useful to write automations to prepare for Yom Tov, or to test / preview logic that is supposed to run on Yom Tov based on sensors (doing that would involve lots of templates).
In fact, you could also add a jewish_calendar.next_holiday service that returns the HDate and regular Python datetime of the next upcoming holiday.
It should take 2 optional paramters:
filter (name or type) to only retrieve specific holidays; this should support substring matching.
after to return the next holiday after a given date (in the past or future).