World Cup squad size

I read that WG can a pick a squad of just 31 players. In 2011 NZ played 4 no 10s -Carter Slade Cruden and Donald. Doubt they were all in a 31 man squad. So have the rules changed?

Dontheman2 wrote:I read that WG can a pick a squad of just 31 players. In 2011 NZ played 4 no 10s -Carter Slade Cruden and Donald. Doubt they were all in a 31 man squad. So have the rules changed?

 No change. 

31 man squad can be named. Replacements can be made for injuries. From 2015:

On 31 August, Wales announced their 31-man squad.
After injuries to Rhys Webb and Leigh Halfpenny during Wales' warm-up match against Italy, Mike Philips and Eli Walker were called up to replace the injured duo.
On 14 September, Eli Walker was released from the squad following injury and was replaced with Ross Moriarty.
On 21 September, Tyler Morgan was called up to the squad to replace Cory Allen who tore his hamstring in Wales's opening win against Uruguay.
On 28 September, Gareth Anscombe and James Hook were called up to the squad to replace Hallam Amos and Scott Williams who were injured in Wales's win against England.
On 11 October, Liam Williams was ruled out of the World Cup having suffered an injury against Australia, and Eli Walker re-joined the squad to replace him. Walker was allowed to re-join the squad, as he was released from the team before Wales officially arrived in tournament.