I think at least next year will have a proper release like last year had. beyond that im not sure. Fantastic beasts films will return so Lego might make some set(s) for that and at the same time surely add maybe 1 potter set.
But after next year potter might have had its solid revival completed.
If sales keep being very good for them and they dont feel the market is saturated, thers no need to stop. Who knows what other franchises lego might attempt in the future though.