to my knowledge, the latest I&P BK ones at 950K were the first dsl houses in a long time to show fatigue in the sales, no more sold out on day1.
there must be others already or coming.
perhaps when we see more of them, we know the market has peaked.
that's when it gets interesting...?

from dev point of view, 3s is built using less land, giving higher density, usually lower $per sqft, more margin than 2s.
some come with lift which will incr price by 150k or so, not forgetting maintenance cost later.
if large family, elderly people will not like 2nd or 3rd level.
large families with adults each driving a car, say 5 cars - think about parking space.
if the row has many cars, imagine the mess along the road.
all these will affect subsale.
majority by far prefer 2s with a bigger space per flr.