One major problem I have with Kinkade, particularly the claim to be "the painter of light" (not to mention the rip-off of Turner, who COULD actually paint) is the fact that Kinkade seemed to miss the fact that when painting "real life", there is only one sun, one light source. If you look at some of his paintings, you'll see what appears to be multiple light sources illuminating the scene. We're not on Tatooine, this is still the earth, last time I checked, and we don't have two suns and three moons.
I think the difference between Kinkade and Adams, as far as commercialization is concerned, is that Adams didn't start cranking out images "in his style" to meet demand - he may have churned the milk a bit in terms of volume production of the same images, but he wasn't going around and shooting a new version of "Clearing Winter Storm" every winter so he could have something for the February page of that year's calendar. That was Kinkade - milk the theme for all it was worth, and then some.
As far as his mark on Art History and critical opinion, in 10, 20, or even 100 years, he may be studied, but he will not ever be regarded as high art. His work does not induce contemplation and thought in the viewer - it provokes a limited range of emotion in his fans (warmth, comfort, nostalgia, "all is right with the world") , and it does so through the repetition of facile, monodimensional symbols designed to reinforce that emotional response. Of course, to his detractors, he also provokes a limited range of emotion, quite in contrast to the one he engenders in his fans. It's throwaway art because it can be digested in a single viewing, and repeat viewings do not generate new insight.