In the worst case scenario, it can indeed happen. Perhaps for some strata it's already happening. Generally it's more relevant to luxury properties as the debt servicing framework appears to have hit them the hardest.
A $1 million property (loan of 800K) requires a nett servicing of $3,600 (assuming 30 year loan of 3.5%) to meet the TDSR of 0.6. Probably $1,500 to $2,000 per month can be paid by CPF (assuming is single buyer). The income to service this is roughly $6,000 (assuming no other loans).
In order for the property to fall to 650K, we have to assume no buyers until the price drops to 650K. The buyers that qualify for the loan of this crash price just needs to service at $2,350. The income to service is $4000 (assuming no other loans). Again, some $1,000 to $1,500 of CPF per month can be used to pay for the mortgage (only assuming individual).
So do consider the pool of people who qualify to buy private and are potential buyers, typically double income families and well to do singles. For private, we also have to factor in HDB upgraders, the profits of which differ from one individual to the next.
Then calculate upwards to $2 million property and assess the pool of potential buyers and their holding power to derive your own conclusion. We have not even started to consider those who own multiple properties, some which have been fully paid off.
The three laws of Kelonguni:
Where there is kelong, there is guni.
No kelong no guni.
More kelong = more guni.