When the Km/K2000 debuted it was available around $400. The Kx debuted at $600 and the Kr, which replaces the kx, bumped that up to $800. The Kx's current price is less a "price point" and more newer items driving down the price of older ones, which is inevitable. Just look at the K7. It debuted at $1300, but you can currently buy it for less than $900. Pentax won't replace the K7 at that price point. They've already replaced it with the K5 which is debuted at $1600.
Something already replaced the Kx, and that's the Kr. The next thing to replace the Kr is likely to be at least as much as Kr when it debuted. Will Pentax introduce another camera line below the Kr? I've not seen anything about that, but if they did it'd likely not be as capable or have as many features as the Kx, and certainly not the Kr.
[edit]All "debuted" prices were collected from
http://camelcamelcamel.com/