Yes, hearing children of completely deaf parents develop normal speech. Some of that is probably because they also have peers in school, etc. who interact with them.
Before hearing aids, cochlear implants, etc., the average person who was born completely deaf only reached a third grade reading level. That is because you need to exercise and develop the auditory part of the brain- if you can't, that part of the brain "dies off" (think of auditory processing disorder). The brain operates on a "use it or lose it" type of principle!
I would never sit on speech delay. I have said this over and over- hearing loss in children can be very subtle and easy to miss. My son had three normal hearing screens (three years in a row) at hte pediatrician's before I got an audiology exam and learned that he is almost deaf in one ear.
My son has always been extremely verbal and articulate. He has never had a speech delay, FWIW.
