The announcement came on Thursday as Japan marked a year to go before the Brave Blossoms tackle Russia in the tournament’s opening game.
Although he won’t be coaching the Sunwolves next year, Joseph will be directly involved in naming his successor.
“I won’t be coaching the Sunwolves next year, but I will be involved in appointing the coaches,” the former All Black told Kyodo Times.
“Next year we need to be peaking in September, certainly not February when the Super Rugby competition starts.
“You can expect a number of our players will not be participating at the start of the Super Rugby competition with the Sunwolves, but they will start a bit later in the season.”
It will be the fourth appointment at the Sunwolves in four seasons since starting their Super Rugby journey.