This response is based on the information provided.  We suggest you discuss with your contract administrator and/or legal department as appropriate. 

FY 2018 NDAA allows for changes in thresholds for various regulations.  The contracting officer does not have discretion to not follow the FAR/DFARS/service supplements.  Should the contracting officer want to pursue what the law is intending, she would seek a deviation to the FAR.  In fact, DPAP will often issue a deviation to allow for the exercise of a change until  that change is codified in the FAR/DFARS as applicable.  The contractor is not bound by the FAR, but is bound by the clauses and terms & conditions of his contract.  So, if the change affects a clause or other terms & conditions the contractor must not act on the change until the clause has been changed and incorporated into the contract.   

There is no definitive language on the subject an you can find disagreement with what we articulated.  Many will state the contracting officer has discretion to act in advance of the change since it is law, citing FAR 1.102(d).  But if a clause is affected, the contracting officer does not have a unilateral right to change/ignore the clause.  That is where the contracting officer could consider requesting a deviation to the existing clause to use the new language in law citing it as beneficial and good business practice until the law makes its way into the regulations.