Seems a bit sudden, wasn't even aware that PTR testing on all raid formats had even been completed.
I guess that no one can say that they are leaving full clearing heroic raiders with too much downtime, but hopefully this hasn't just been rushed out for the sake of that - from the look of this thread, this announcement isn't ideal. (However, I'd those complaining because they "lost steam" and then only recently picked up don't really have much reason to do so.)
With a 16 boss tier I'd have expected a bit longer before the release for sure