If you look at young and old O-Tsuru you'll see the same difference. I think Oda is making the traditional Japanese characters take on the ukiyo-e facial style as they grow older.
If you actually look at Kyoshiro's hairline it's similar to Denjiro. Also his silhouette is the same but with the pompadour backwards. It's all circumstantial at the moment but he's the most likely candidate.