First of all, remember those pics are from a truck with a leveling kit installed, which raises the front end 2". The reason these trucks have a rake from the factory is so that when they are loaded, as shown with the camper, the front end it not in the air.

Most truck campers I can find that will work on a 1/2 ton truck are about 1500 lbs, which shouldn't cause you to sag much in the rear. Especially considering the overhang most have over the cab actually shifts a good amount of the weight on the front axle.

Unless you plan on towing something heavy, in addition to your truck camper, air bags shouldn't be necessary.