Yes, it is true that cognitive instruments can only be administered once every TWO years. There are other instruments that could be used for the cognitive portion of a comprehensive assessment, in a child of this age, such as the DAS-II and SBV. If it seems that a comprehensive assessment is indicated immediately, and you also want to reserve the WPPSI-IV for kindergarten entry testing, you could mention this concern to the evaluator, and request that they use a different cognitive instrument.

...pronounced like the long vowel and first letter of the alphabet...