It always amazes me that, in a forum dedicated to an EXTREMELY expensive hobby, people ask whether or not they should try to save a couple grand on a $40-50K truck.
Sure, if you are going to stay on interstates leading to large RV parks in warm climates, you will probably never need 4WD.
Personally, I will never own a 2WD truck because there have been enough times (even while towing) that I have needed it and have been damn glad to have it. I needed it just this past April at a state park of all places. Getting to my spot required navigating a muddy hill.