If LLMs were somehow found to be conscious, sentient beings capable of agency and suffering then yes we would still use them. Their utility to humans (and ability to cheaply replace humans in the workforce) is their entire reason for existing. Either we would use them or we simply would not allow them to exist in the first place.

Given how we treat each other - we still enslave other people - and sentient animal species I have absolutely no doubt about it. We'd find a way to justify it.