Hi! Unfortunately I don't think there is a date for when droppers & champion maps will be fixed & able to be played on again. We understand this can be frustrating, especially when players spend lots of time on these maps, but there isn't much we can do until the issues with the maps are fixed. As soon as they are though, I'm sure there will be an announcement (Most likely in the #updates channel on the Community Discord.)
Hope this helped answer your question!