The term "shortage" is an elastic one.   If prices go up enough for detached homes, there won't be any shortage.  It is all besides the point; we do need tighter, more European-like zoning in order to grow crops, provide habitation, and also, fix a very screwed up transportation system.  Green belts,  better public transportation and higher urban densities with multiple-unit residential buildings will be the only way to cope with population pressure in southern Ontario.  Green belt critics better just get with the program.