As I understand it, dip and pack is meant for basically pests etc not to be exported or imported and really has no preservative qualities to speak of as far as trophy care. They would likely have them tanned shortly after receiving. My taxidermist i use for north American game has stored his own tanned hides in a freezer for 10-15 years and said they mounted fine. Untanned and frozen they would last not nearly as long.
Just ask the taxidermist what arrangement they are willing to work out with you, as the tanning is going to be a cost they are likely going to incur almost immediately. Should be covered by your deposit, but some may be more or less accommodating to this type of arrangement, not sure there
