Thank you for the question.
The short answer is that once the wills provision in the Indian Act is repealed, then the provincial definitions of common-law partner would prevail vis-à-vis wills and estates regimes in their respective provinces or territories.
So you're correct in that the Indian Act definition of common-law spouse would remain for the rest of the Indian Act, but the regimes that would apply to wills and estates would be the provincial regimes. Therefore you have to look to whatever the definition of common-law spouses is in a particular provincial regime for wills. That would be operative.