Rperez: define "a long time."
My iPhone (the original) stopped being supported at 3.1.3 and by the time iOS 5 came out -- about two years later -- there was basically nothing new available for it.
Presuming the original poster meant a fourth-generation iPod Touch (ie one generation behind the current model), then yes, iOS 6 is as high as he can go, and it should be good for another year or two, app-compatibility wise.
After that he'll want to slowly stop updating apps and just leave it as-is app-wise. It will probably continue to work for several years after that if he's good to it (my original iPhone still works fine, though I don't use it much anymore).