There are ways to make buildings more flexible so that adjacent units can be combined.  I've heard of this in the past but it's not that common.  
Today's condo market is populated largely by singles and young people.  That may change in future as they have families, but there are also predictions of an older population who will own condo's in the city as a getaway from their cottage (which would be a principal res.)
To ensure flexibility would take leadership from the city/province in terms of flexibility in condo declarations and in original construction.