The official twitter account of One Piece announced that Saori Hayami will play the role of Yamato on the said anime series.
On the said announcement, Yamato will appear on the episode 990 on one of the longest running shounen anime in Japan. Episode 990 will broadcast this September 5.
Yamato also appeared in the video “ONE PIECE Vol.100 / Ep.1000 Celebration Movies” WE ARE ONE.” which was released last August 31 prior to the 990th episode of the said anime.
Source: Dengeki Online