What could keep the property market in check for the rest of 2017?

Reduced outflows from China is one factor.

According to Natixis, taming the property market remains an uphill battle for the government. Residential price further accelerated in March (+17.8 %YoY), with prices of smaller flat significantly outpacing their larger counterparts.

In response, HKMA recently announced tightening measures, which mainly lowered the loan-to-value cap for borrowers with one or more mortgage loans and cut debt servicing ratio of borrowers with income mainly derived from outside of Hong Kong.

Here's more from Natixis:

Such prudential measures, together with reduced outflows from China, should keep the property market in check for the rest of 2017. Regarding financial conditions, HKD and CNH HIBOR went down in May along with a slower rates tightening cycle expected in the US and RMB’s stabilization. The relatively clam RMB market also reined the fall in RMB deposits in Hong Kong.

All in all, Hong Kong’s rebound in external trade and retail sales are mainly cyclical and we expect GDP to grow at 2.5% in 2017 (2016: 2%). Yet with structural issues like increasing competition from mainland in the sectors where HK has the largest comparative advantage, and an ageing population, it will be hard for the HK economy to keep its growth momentum beyond a few quarters.