Check out my post on the death of the H2 Hummer for my ideas on the Tahoe/Yukon, Suburban/Yukon XL, and large pickups:
Jalopnik: GM Killing Hummer H2 After 2011
There are people than need room for numerous passengers. In their case, wagons, minivans, and CUVs are better choices, in that order. There are people that need room for lots of cargo, again the same vehicles are better suited or a pickup is in order. There are people that need to tow heavy items. Most of them
want rather than
need to tow their boats, camper, or other recreational vehicles a few times a year. They may be better off renting something for those few days than using more vehicle than is necessary the rest of the year. For those who still want to tow with their SUV, I think GM can meet those needs with a creative option on a lighter unibody. There are those that
need to tow for work reasons, and they probably already use a pick up truck. Then there are those that require off road prowess, and that can be met with ground clearance in a smaller vehicle. For the small few that can't use any of the preceding vehicles, a single large Hummer should suffice.
When you combine all of the above requirements: passenger space, cargo space, towing, and off roading, I think that there are very few people who would say they need all 4 in one SUV. Especially when it comes at the expense of fuel economy, ride, handling, seat storage, or the ability to excel at any 1 of the 4 tasks. As gas prices go up, many people are seeing this very thing for themselves and are looking to alternative solutions.