The decision means that the tournament will equal the record number of teams, with 16 nations having competed at the 2000 World Cup, which was staged in the United Kingdom, France and Ireland.
In 2008, the event featured 10 teams, and the most recent tournament, held in England and Wales during 2013, saw 14 nations participate.
Australia, who are the reigning champions, are due to co-host the 2017 World Cup with New Zealand and Papua New Guinea, where 14 teams will again be present.