I was extatic many moons ago when I got my first tricycle. I don't think it is just marketing that made me want something with more modern features
The D200 (bought in 2006) was much better.
I can still eke nice low-light images from my D200 at ISO1600. But I happen to shoot moving subjects and want to keep all of the D200 features, with an extra two stops of low light hi-ISO.
The D7100 has the extra two stops. But it downgrades almost every other feature!
If I was influenced by Marketing, I would have been trying to get the extra two stops with a D300, a D90, a D300s, a D7000, a D7100, not counting all the FX bodies (which I don't want) but then would have to give up too much for that, in features or money. And many in the same picture taking situations feel the same way.