Like I stated, the only reason I can see it bust is if a LOT of people at once get forced to sell for some reason (most likely because they can't afford to pay skyhigh mortgages because they all at the same time loose their jobs and the mortgage companies are at that precise moment looking for cash infusions and demand instant payments) while at the same time there's few people looking for houses (because they can't afford to buy most likely or are wary to because their own job situation is insecure).
Something like that happened on a small scale a few years ago but it was at the time not enough to cause prices to drop (it did cause a marked reduction in the rate at which prices were increasing though).
At this time (at least in this country) there's a surplus of midrange houses combined with a shortage of lowend and highend houses. This causes houses in the €220-300.000 range to be slowly dropping in price (but no more than a few tenths of a percent a year) for the first time in decades (house prices here are astronomical as it is, that price gets you a 100sq.m. house with maybe a small garden and if you're lucky a carport or reserved parking spot on the road).