Thank you all for your input here. I'm pulling a boat, not an RV ... perhaps should have included that in original post. The boat is 23 feet, so the trailer + hitch = almost 30 feet long. Double axle. Boat weighs 4500 lbs, trailer weighs 1600-1800. With gas and gear, total weight can approach 7000.
I tow the boat from Bay Area to Tahoe ONCE in May, then back ONCE in October. In the winter, I occasionally tow it in the flat to launch in the SF Bay. So, as you can see, the low frequency of use of my tow rig motivates me to potentially be able to retire it. However, if the Touareg (or Cayenne) cannot not safely or effectively make the trip up to Tahoe, then I would just keep my Suburban for those needs. In that case, I will probably buy a different small-SUV for a "family car" and not worry about towing with it.
Any further thoughts or opinions would be appreciated. Thanks