Notwithstanding sub. (6), for natural persons, fiduciaries, trusts and estates, at the taxpayer’s option, “internal revenue code”, for taxable year 1986 and subsequent taxable years, includes any revisions to the federal internal revenue code adopted after January 1, 1986, that relate to the taxation of income derived from any source as a direct consequence of participation in the milk production termination program created by section 101 of P.L. 99-198.