Oda made a comment on the manga’s future in Jump Festa 2016 which was held on 19/20 December:
“My readers ask me “When will Sanji appear?” again and again these days. Hirata-san (Sanji’s voice actor) also asks me “When the heck will Sanji appear?”
Next year is Sanji’s year!
Finally it’s time to reveal the mystery about Sanji’s birth! The Straw Hats who didn’t made much appearances in Dressrosa Arc will have many highlights next year.”
This means awesome moments for Sanji, Nami, Brook and Chopper! I’m now seriously hyped for 2016! *__*