Another proof about why Shanks is a Celestial Dragon comes from history and near the end of the Marineford war. Well, we saw that when Yonko Shanks appeared at the scene, he said once that stop this war and even Sengoku replied that he is ordering the war to be stopped only because of Shanks. Shanks stopped the biggest War the world had ever seen back then just by his mere words.
Well, these two instances prove that Shanks indeed is a Celestial Dragon as he is doomed to have Celestial Dragon lineage. This opens up a possibility of a lot of things. Who does Shanks want to talk about? We saw Shanks saying that he wants to talk about a certain pirate. Now, who is this pirate that Shanks is so desperate to talk about? In my opinion, this pirate has to be the captain of the Rocks pirates.