Make the Tundra bigger, wider and a taller. Stretch the wheelbase.
Give it more powerfull engine: long-stroke for more low-end power, more displacement (5.5L or bigger).
Id also like to see an option of a 3/4 ton Tundra with a diesel, solid front axle and all in all just a beefier Tundra for people who want Toyota reliability but need something with a little more "giddy up go".
Id also like to see a Tundra TRD (something like the SVT Lightning or the Ram SRT-10). Basically, do the same thing that Toyota did with the Tacoma X-Runner, but give it at least 500 hp. Im tired of Dodge bragging about having the word's fastest production pickup when I know that Toyota can do better. All Dodge basically did was cram the Viper's V-10 into a 4x2 Ram and give it a slight suspension lowering. If Toyota can make a Tundra with 500 hp and work the same suspension magic they did on the X-Runner, that would be one sweet truck.