World Rugby boss Brett Gosper has said a future World Cup could enlarge the number of teams taking part without losing competitiveness.
Both England 2015 and Japan 2019 will have 20 teams, but 2023 may be larger.
Mr Gosper said allowing fringe nations into the event would allow them "to promote the sport in their countries".
"As the sport grows and we conquer new markets the discussion is about looking towards expanding [of the World Cup], rather than contracting," he added.
'Fast growing'
A larger World Cup would offer the chance to sell the sport into new markets, as well as increasing the potential revenues from the tournament in terms of TV deals, sponsorship, hospitality and ticket sales.
He said a larger World Cup would not necessarily mean teams playing more games, as tournament groups - which currently have five teams in them - could be juggled in size.
Mr Gosper said rugby union was growing strongly around the globe, but particularly in the markets of the US, China, India and Mexico, with Russia and Germany also growing nations.
"Rugby is the fastest growing team sport in the USA," Mr Gosper told a Sport Industry Group Breakfast Club gathering of sporting executives in London.
He added that although Germany and Russia also offered potentially huge new TV markets for the sport, 2019 was not considered the right time to expand and bring them in.
