Precious, one of the longest serving members of the Dragons coaching team, will link up with Russia coach Lyn Jones and the Bears as they head to Japan next year for the showpiece event.
Russia face Japan, Ireland, Scotland and Samoa next year in Pool A at the World Cup.
The Bears open the tournament against the hosts at Tokyo Stadium on Friday, September 20.
"Will has been one of the longest serving Dragons and has an opportunity to go to a World Cup," said Jackman.
"Given his service to the Dragons, we have decided to give him a sabbatical for a year to allow him to take up what he sees as an unbelievable opportunity.
"We want to be an organisation that looks after people properly, so he will have a sabbatical and will come back to us post-World Cup."
Dragons face Russia at the home of Bedwas on Friday, November 16 (kick-off 7.30pm). For ticket information click HERE
