Eiichiro Oda loves working on One Piece as evident by his prolific output during the ongoing shonen series' last 20 years of serialization, rarely taking time off or delaying chapters. As such, Oda didn't attend Jump Festa 2018 but did send a handwritten message that was displayed on screen during a One Piece presentation. He reportedly promises fans that the series would start the Wano Country arc next year, something he actually said would occur this year at Jump Festa 2017 last December. He apologized to fans for not delivering on his previous promise.
More interesting, Oda teased that introduction of a new villain, who's been a lurking legend up until this point until this series and that this adversary "may or may not" be related to Whitebeard. Whoever he is, he'll be Luffy and the Strawhat crews biggest foe to date and his arc will make the Paramount Wars look "cute" by comparison. As intended, One Piece fans are analyzing and debating Oda's comments and are split on whether he's referencing Vegapunk, Kaido or Weevil.
As of July 2016, Oda stated that he's completed about 65% of the story he wishes to tell in One Piece. A somewhat dizzying prospect considering the series has been running for so long that is has several Guinness World Record and 87 published volumes. To put that in perspective, the anime adapting the manga currently sits at 816 episodes and is several volumes behind where Oda's currently at in the Shonen Jump series.