If your current home's assessment feels too high relative to comparable sales, the City of Saskatoon's Board of Revision is the formal channel to appeal it before you sell, which can matter for your net proceeds even though it will not change what the buyer eventually pays.
The Homesteads Act, 1989 protects a spouse's interest in the family home during marriage, but it is not a tax mechanism and it has no effect on the property tax bill for whoever owns the smaller home after the move.
Confirming your realistic sale price and the new home's likely assessed value together gives you an honest picture of what actually changes when you downsize. Get your hand-reviewed valuation from Joel Dyck.