Answer is yes as long as the task order is issued before the IDIQ contract expires.  The FAR only requires that orders "be within scope, issued within the period of performance, and be within the maximum value of the contract." (FAR 16.505(a)).   There is no requirement for the order completion date to be within the ordering period of the contract.  Only that the order be issued within the contract’s stated ordering period.  And, as you mentioned, FAR Clause 52.216-22 says as much as well: “any order issued during the effective period…but not completed within that period shall be completed within the time specified in the order”).  A blank date for the fill-in in FAR 52.216-22 shouldn’t be an issue as long as the government and contractor mutually agree on a completion date for the task order.  Also, make sure that sufficient funds are available, and the order's period of performance does NOT violate fiscal constraints for use of OMA funds (I'm assuming the contract is funded with OMA since you said it's for services).  For example, OMA funds are only current for one year, although for service contracts that year could be 12-months that cross fiscal years (ref: 10 USC 2410a).  Finally, it’s always a good idea to discuss questions related to scope, performance period and/or funding of a task/delivery order with your Contracting officer, legal advisor and Comptroller.