The Welsh, who still have to complete their Six Nations campaign, are scheduled to play Japan on June 27 and then two tests against the All Blacks on July 4 and 11.
"It does seem unlikely and, as each day and each week goes by, that seems more and more the case," Pivac said.
"But until it is called off, or postponed, we have to prepare as if it's going ahead and that's certainly what we are doing."