Yes, the Demon's ability will trigger.
Once we get to the step when the spell is considered cast, the Sculptor's effect ends, and the Demon is back to normal and has its triggered ability. The Sculptor's effect ending just happens - it doesn't use the stack, it just becomes a creature again with its abilities as soon as the creature spell is considered cast. Then, we check to see if anything should trigger from the creature spell being cast. The Demon has a triggered ability that would trigger, so its ability triggers and you'll have to sacrifice a creature.
Nathan Long
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