Nobody went through "lineage factor" possibility ? Oden Artificial Fruit.
Same as Momonosuke turning into Kaido's fish form once in a while,
there would be a character turning into Oden once in a while.
Oden is definitely dead. It could be some sort of trick, but if somebody wanted to harm Scabbard's, he or she would do that when there were unconscious. It's probably someone with good intentions, maybe even ally.