The parents are hearing. My guess is they know nothing of ASL. And the baby can hear sounds with a HA, so it's not totally deaf.
If deaf parents have a hearing baby, and the parents can't talk, how are they going to talk to the baby? Same as for hearing parents having a deaf baby, they don't know ASL.
Some hearing children of deaf parents who can't speak, are behind on their own speech, since they were taught ASL and not speech.
If I had a deaf baby, I would expose him/her to both worlds. ASL, and talking. But I would not expect the baby to talk normally, that would take years of schooling.
It's a "new world" for hearing parents that have a deaf child. I'm sure, in time, they will learn more of the deaf culture as their child gets older...and I'm just as sure that when a deaf parent, who has no speech, has a hearing baby, they will want to expose the baby to sounds and speech and also ASL.