A (thinly-traded) bet on prediction market Intrade is as follows: "Monthly House Price Index for Vancouver to be 121 or less before the end of 2013". The "House Price Index" is the Teranet HPI. The Vancouver Teranet HPI is currently 170, roughly at its all-time high. To hit 121 means a 30% drop in about 16 months for this bet to pay.
If Vancouver were to follow the US's trend the chart below showing HPI changes from peak gives some indication at how precipitously Vancouver's HPI could drop below 121. Note that the US cities did not experience house price crashes at the same time -- Seattle most notably was delayed by about a year or so -- but look at how closely the brunt of the price drops were aligned from peak, roughly 12-24 months after.
The graph below includes two measures for Vancouver, one with the peak at June of 2012, the other with a "shifted" de facto peak of August 2011. This was done because as one can see from the US cities the peaks were followed by about a year of mulling near or at peak prices before dropping significantly. If one assumes that the actual "peak" for Vancouver was August 2011 and the HPI is now at the advent of that "Wile-E-Coyote" moment, the pregnant pause before the big push downwards, one could think Vancouver has a fighting chance to hit the "121 or less" threshold before EOY2013 target.