All intersting points. However, as a Denverite and having been to many cities such as LA, NYC, etc, I can tell you we will in NO WAY ever become the messes they are environmentally, population-wise, or anything else. Thankfully we are light years ahead of most american cities when it comes to mass transit. Denver will have, by 2015 (Fastracks), more than half a dozen rail lines spanning over 200 miles of track across the entire metro, from Boulder to DIA and Longmont to Lone Tree. As it is right now we have seen a drastic increase in RTD ridership because of the popularity of the TREX project, and many people are commuting instead of drving despite I-25 now being 12 lanes wide. Also, we have a bit of luck on our side as infill is our primary growth at the moment. The closing of Stapleton has left a grand swath of land within the Denver urban core, and much of Denver's growth is attributed to the building in this zone, which is urban focused in nature (NOT houses or Pleasant Valley Sunday, but row houses and condos with commercial centers footsteps away, and in some cases even mixed).
Furthermore, despite seeing phenomincal growth in the North Metro regions (Greeley, Erie, Dacono, etc) the suburbs are much more meticulously planned to incorporate denser projects as well. Rather than slap down a plethora of winding cul-de-sacs and 1.5 acre yards, the neighborhoods have almost regressed to a gridlike system, and as said earlier, houses are smaller, closer, or in many cases, attached like in a rowhouse close to commercial zones. This is not to say that the classic suburbia is not also being built, but at least there is consideration of other building alternatives so that buildings don't gobble up land like weeds.
So long as Denver continues to emphasize 'core living', dense development, and keeps its head poised forward into the future on the matters of transportation (not 16 lane freeways) and water, we will do fine.
If you have any concern of sprawl, my only concern is Aurora
. The beltway doens't slow IT down, that's for sure. Anyone from Denver wish to chime in on Aurora's case?