Umm, just to clarify some things:
Theoretically, you could find any genetic morph in the wild - that's where the genes came from. But not many morphs exist in the wild, because of the very low probabilty of 2 snakes with the same genes breeding, and the very low likelihood of morphs to make it to adulthood and breeding age. Amels would have pretty much a 0% chance of reproducing in the wild. Same with most others - especially amel-combination morphs. Even if a snow happened to hatch in the wild, it would be too different from everything around it, and would look like a good target to predators.
Normals and anerys live in the wild - and thrive, grow to adulthood, and reproduce. There's probably some charcoals, too. And hypos would probably also be able to survive. Amels have probably a 0% chance of living to adulthood in the wild, even though they are probably born every once in a while.
So, I'd say you're pretty much right. I'd say at least 99% of corn snakes in the wild are normal. The ones that aren't normal are usually concentrated to specific localities.