The 2018 Dream Team centre was forced off in last weekend's 33-22 win over Salford Red Devils.
He has been left out of Wakefield's squad for tomorrow night's clash against Huddersfield Giants and will require surgery before he can return to action.
It comes as another major blow to Wakefield and head coach Chris Chester, with prolific winger Tom Johnstone already out for the season.
Craig Huby, Tyler Randell and James Batchelor are also long-term injury concerns for Chester.
And the Wakefield boss felt that something should have been done about the tackle that forced Tupou off the field on Sunday.
"He will go for an operation early next week, we are probably looking at about three months," said Chester.
"I said it at the time, and I still think now that something should have been done with the challenge.
"A guy has had his leg taken away from him and gone past the 90 degrees and it has caused a hell of a lot of damage in his groin.
"For us to lose Bill and in the manner that we have lost him, and there is not going to be any charge, it is really disappointing.
"We have lost Bill, we have lost Tom, I think that is five or six long-term guys now.
"When we see you the challenge on Bill and to lose him for that amount of time is one [thing] and two is that nothing has been done about it.
"We are very frustrated. As a coach I am frustrated and as a club we are frustrated."
Chester says the club will now need to look at bringing in some new faces to bolster the squad.
He added: "We are going to have to look at reinforcements now, we are literally down to bare bones.
"In terms of the pack we are great. Our pack has been the big plus over the last few weeks.
"But to lose Bill and Tom means we need to find 300 metres from somewhere per game, that is not easy to replace."
On Tupou's injury Chester added: "It has come away from the bone, it is not good."