One of the impacts of the growing value of real estate is higher property assessments (via MPAC) which means higher property taxes - assuming the mill rate is unchanged.  Land transfer income (local and provincial) also rises. With this easy added income, I do not see any incentive for local politicians to  act.  
Realtors are perhaps envisioning added inventory when property taxes become too onerous for those living on the  edge and they have to sell, i.e. 'house poor' seniors living in family homes.  In the words of Liberace, they 'will cry all the way to the bank'