I'm excited about the possibility of new brackets getting new activity in Legion, but 19s was the only bracket to maintain strong activity pretty much throughout WoD. It's undeniably been the main twinking bracket for awhile.
39s had a nice few weeks.
The only other bracket that saw activity the whole patch was 29s, but the player base kept moving around from 20 f2p, to 20 vet, and finally to 29 at the very end of the expansion. It was just all over the map in terms of player base.
I'd like to see if we could get a mid level bracket going in Legion, but I don't see the point in trashing 19s. 19s kept this whole twinking thing alive.