The world map is procedurally generated, but not all of it. Reportedly, some aspects of the map will be static, such as story-related locations. But the rest of the world will have a unique quality to it every time you log in to play.
This means that players will be able to go back to the previous locations they've been before and find a completely different layout of the map with a totally different set of crates. This guarantees a high replayability level of the Minecraft Dungeons.