Plumtree, 23, the son of former All Blacks assistant coach John Plumtree, was born in Wales and is about to join the Scarlets to prepare for their 2023-24 season.
A former New Zealand Under-20 representative, he made his DHL Super Rugby Pacific debut for the Blues in 2021 and played six games for the side. Able to play in any of the loose forward positions, Plumtree could be useful for coach Warren Gatland.
The retirement of Justin Tipuric and Josh Navidi and the unavailability of Ross Moriarty and Josh Macleod has left Wales with fewer options in the loose.
Also in the loose forward area are Plumtree a, Dan Lydiate, Jac Morgan, Tommy Reffell, Aaron Wainwright, Taulupe Faletau and Christ Tshiunza.
Gatland named a 54-man squad to prepare for the Cup, but only 44 are available to travel to Switzerland this week for a two-week pre-Cup training camp.
BBC Wales said it was expected that Plumtree would join the group.
Wales will have another camp in Turkey later this month and then play warm-up games against England and South Africa.