It's a problem of false dichotomy. Sentience isn't a light switch. It's grains of rice that accumulate into a meaningful mass. This is also the reason the abortion debate will never be resolved. We can expect similar passion ex uncertainty from the future machine sentience debate.
> It's grains of rice that accumulate into a meaningful mass
Suppose we could temporarily reduce these grains into something very small. For example, putting a human into deep anesthesia. Is it immoral to destroy their body at that point in time since they are less sentient than an insect?
Or do we consider their potential for sentience, as they can hypothetically be removed from the state of anesthesia in the future?