Regarding the NPD survey, my two concerns are such:

1) For all intents and purposes, the NPD is looking at buying habits as opposed to playing habits.

I don't know the specifics of their survey, but I would argue that you have the equivalent of the "whale" in the retail space. This whale is the early adopter of all new hardware and buys all the hyped up AAA games. Most people are likely picking and choosing which games and consoles they buy, and sticking with those decisions, and when it comes time to tighten their belts, they still play games, they just don't buy new ones as often. Given the price of your average freshly released AAA title at retail, it doesn't take a lot of these whales to make a dent in the sales charts.

I know plenty of casual gamers who play games All The Damn Time, the only difference is that they're not constantly buying new games, they found what they liked and they stick with it, and for that reason they're not showing up on the NPD's radar.

It's worth remembering, realizing that not buying is not the same as not playing games is what allowed Nintendo to fill a vacuum and dominate the market after the western games industry completely jumped ship.

2) How people use this information worries me greatly.

So you now have a particular subset of core gamers being explicitly told that they're the primary revenue source for the industry. This particular group is already very vocal about what they like and dislike from their games. If the industry takes to heart that these people are the ones to be strip-mined, changing the ending to Mass Effect is only the beginning.

Just look at the situation in Japan right now, where a particular subset of creepy okatu is all but guaranteed to spend absurd amounts of money on a particular subset of creepy moe games and merchandise, and entire companies like Idea Factory just cranking out one horrifying piece of crap after another to cater to this crowd, and general trends in that company have been all but much worse for it.

Okay, so that's a bit of an extreme example.

The point I want to make here is that if publishers perceive the whales as being the money makers, and the whales themselves use this fact as leverage to make even more demands of the publishers, then trends in games will continue to homogenize towards whatever this vocal minority wants. Diversity could end up eroding, and we'd all be worse off for it.