No it's not. It's a predictive algorithm. A highly sophisticated one, but still just that. If it were sentient, hosts becoming sentient wouldn't have been such a big deal.
Serac might have treated it like a sentient entity because he saw something of his brother in him.
Anyway, i liked it. RIP Dolores, RIP William and, of course, RIP Rehoboam. We hardly knew you (but you sure knew us).
I assume Bernard woke up in the same timeframe we saw old Host-William at last season's post credit scene?