There are two approaches...
1) I won't ever buy a 1 ton truck/ and or transition to a larger camper... Buy a hitch for your camper. I bought a 15k Pull Rite SuperGlide... My camper is around 9,800#... 1.5 safety margin :). Plus whatever the hitch manufacturer throws in for safety.

2) I may one day get a larger truck, camper, or both...and don't want to have to buy another hitch. Buy a hitch for the rated capacity of the tow vehicle, current or planned...and you can pull anything it's capable of.
Really becomes a personal choice. No wrong answer.
So, I will probably have to do this someday...I can foresee getting a New 1-ton truck...and a larger Toy Hauler down the road sometime... I will have to buy another hitch. We didn't know how much we would enjoy the RV lifestyle... We have had our 5th wheel since June 2010...and spend over 60 nights a year in it (averaging about 6 nights a month). When I retire, we will be going places far beyond the reach of our current locations... Cannot wait!! 3572 days...but who's counting???