I agree - it depends on the social community, much like if they adopt a child from China but don't speak Chinese. You can learn Chinese. You can take the child to China later. But the child would culturally be American. Would it be better for him to grow up hearing in a hearing home?
We have a friend who lost his hearing after an infection and has an implant, and he can hear, but not 100%. So the child will still be "hard of hearing" to some extent. If the child is not going to culturally be deaf, then I would want to get the implant. The child can be encouraged to explore deaf culture, and I would learn and teach the child sign (which is beneficial for hearing children, too) and kind of treat it like one would an international adoption, culturally speaking. Knowing it will NOT be the same, but giving the child some information.
FWIW, sometimes our friend with his implant turns it off, just to have silence, or to feel the bass of music (many deaf people like music with heavy bass) without any other influences. He also prefers to text or email instead of use a phone, and lip reads to an extent. For him, even the limited hearing provided by the implant has been important and this child would not know any different. I think it is important to remember that it won't be "the same" but will it give said child the advantages his parents want? And if they choose not to, will they (as presumably hearing parents) be immersing themselves and their child into the deaf culture or will he be a deaf child in a hearing culture?
I watched a very interesting show late one night (I think produced by Galludette, which is rather local to us) which touched on someone who wanted the implant as a college student, which of his friends agreed or disagreed, and the experience of a student who was from some rural place where he wasn't immersed in a deaf culture, though he was deaf and spoke only in sign. He was a fish out of water on campus, because the deaf community had not factored much in his childhood and growing up experience. I suspect he would have rather had the implant as a child.