As you know, you're right at the top of the capabilities of a gasoline powered truck. If you're not going to be towing very far and if you're not in too demanding of terrain, your truck will probably do the job.
You might consider switching up to a 3/4 ton diesel if you're going to be traveling farther and in rougher terrain. They're good for kingpin weights up to 2500 lbs. and a trailer in the 12K lb. range.
If you think you'll be going to a larger fifth wheel trailer, there's no replacement for a 1 ton dual rear wheel diesel.
