If BoP-HQ does become profitable, I don't see it becoming so super-profitable that a sequel is guaranteed.
This will end up being an on-the-bubble situation at best.
If it does get a sequel, it'll be PG-13 for sure. They might do the opposite of Deadpool, and release a PG-13 cut for theaters and an unrated cut for home video/streaming.
This is probably what they should have done in the first place.
Oh, and "Harley Quinn" will be at the top of the title. No more burying the lede.
Furthermore, Birds of Prey by themselves without Harley won't get anywhere near a sequel. It seems they might have been trying to spin two franchises out of this, but no way that'll actually happen.