I see a lot more turkeys than I used to. However, it doesn't improve my chances of killing one all that much.
Turkeys do not have culture. They can't read or write , and turkey bards do not go from roost to roost yelping out turkey ballads (at least I hope not), so it's hard for the boogers to pass on what they've learned. Turkeys are not any smarter than before, but they're probably exposed to humans more. I'd say they're more exposed to stupid turkey hunters as well. It doesn't take many shot streams going over a gobbler's head to give them the idea that they should be a might more careful.
There was a discussion about this many years ago in relation to fish. It used to be that you could saw off a teaspoon, hang a treble hook off of it, and make a dandy bass lure. Then bass stopped biting at teaspoons. They didn't learn. It wasn't like daddy bass didn't come home one day and mom and the kids lauched an investigation. The problem was all the easy fish got taken out of the population, and you had fish left that were somewhat predisposed to bite at teaspoons less and less. Perhaps that is happening to the turkeys as well. Who knows? If there is an evolutionary pressure it would be my guess that it would predispose gobblers to come to calls less-- that whole turn nature on it head thing. However, I honestly don't think that will happen.
I think each gobbler has an imprint in his head of a hen's call. When he hears something like it under the right conditions, he's coming. As a turkey gets older and survives a few seasons, he's going to be less likely to come. I think older gobs add some experience to their response. However, I think that once that trigger gets tickled inside his brain, he's going to come.