This is what I think.
Law is dead but his soul remains. The only proof for that are the last words on the last page of the latest manga. There's a voice saying: "Listen up Strah Hat-ya!" Law is the only one calling Luffy like that. This could be possible since we don't know the true powers of the Ope Ope No Mi yet. I assume it's him and in the next chapters he's going to help him defeat Doffy.