House price in a well developed area is determined by many factors, such as land value, oil price (most of the construction materials are made of oil by-products), labour cost, building code, etc.
There is an example of decreasing house price in Detroit. It's mainly because of crime rate and unemployment. However, it's less likely to occur in Ottawa because the main industry here is high tech R&D, plus jobs in the federal government. A slow down of price hike is more likely though.