The central bank won't let housing prices go down significantly, so rate will not increase rate back above 4% for a while.
The cannot stop. At least not with the current currencies.
The Central Bank could just buy the mortgage bonds by putting the mortgage on the asset side of the book and issuing currency on the liability side of the book. The Bank of Canada only does this to manipulate the overnight interest rate, on Government of Canada bonds. However, all rules have been thrown out the window these days.