That would probably mean apartments, but Mormon families still tend to be very large (very very large by the standards of non-Mormon families) and they typically want large backyards for their kids. Maybe someday that will change, but not soon enough to make a material difference in our lifetimes.
I think you'd be surprised. Mormon families are still larger than average, but there are plenty of Mormon families with just one or two kids. Not to mention that there are going to be plenty of "pre-kid" adults, or empty nesters around, and they need homes too. What reason is there to make most of the land exclusively single-family homes on big lots?
2. You can still have access to a backyard with multi-family housing. Where I live now in Munich, you have lots of small (or large) apartment complexes with shared backyards that kids play in all the time.
3. There's all kinds of ranges of housing in between "single family home with large front and back yards" and "massive apartment block surrounded by sea of asphalt". Duplexes, 4-plexes, and townhomes all make for increased density.
In any case, why not loosen the regulations and let the market decide? If there really isn't demand for apartment buildings, then developers won't build them, since they like money and all.
