I'm not sure a house in cabbagetown has much to worry about, although if it were me, I'd sell first thing in May.
As for the new mortgage rules, the real crux of what they will do has to do with the investment market. Now, unless you have 20% down, you're not allowed to buy an investment property and that's what's been driving this most recent condo surge. I wonder, considering sooooooo many of the new condo's coming online within the next 18 months are investment (i think 40%), if this will force people to sell. Maybe they bought 4 units at 10% down and now need 20% to close the transaction - what will this do? Is the change grandfathered? How can they grandfather something like that when nothing has technically been bought or sold?