It is possible to generate a fully playable map that is unique. It just requires a LOT of boundaries for the generators. For example, saying "Fill my land with terrain between -128 and 128 units high" won't work. You have to use a complex mix of calculus and greater level mathematics to generate the terrain. Think of it like saying to the map generator "You can use curve functions up to this magnitude" and then applying a certain random face generator to roughen up the curve created by the smooth function. On top of that, you also need to put in rules that separate higher terrains from lower to create valleys that allow for entry, otherwise you may end up with completely walled off sections. With plenty of restrictions in place, it IS possible to generate 14,000 maps. However, such a technology has not ever really been implemented on that high of a detailed scale. The only game to use similar restrictions is minecraft, and it does not NEARLY have the kind of generation restrictions that dust would need.

In all honesty though, just generating a playable, fully explorable map does not mean that it will be good. Think of the countless maps created in the past throughout FPS history that had MAJOR advantages towards offense or defense. Even dev created maps can be unintentionally favored to one side or the other, so if we don't even know the *formulas* for a perfectly balanced map, we can hardly create a algorithm that will produce for us a thousand perfect maps.

TL;DR : The sad truth is it is too complicated to generate truly unique terrain that is balanced for gameplay. Most likely we will just end up with randomly generated terrain, and maybe a few jumbled default turret locations.