The planets are already detailed. Gas giants need some work (they look OK, but you can land on them), but rocky planets have a huge variety of terrains and atmospheres. We currently only have cities adjacent to starports, but the long term goal is to have many unrelated cities dotted about the place, proportional to the listed system population.
We already have NPC ships flying about the universe. While you might see traders near space stations, pirates do also exist. Unfortunately, space is very big, and while pirates might try to chase you, you're unlikely to ever see one. We're working on designing around that, with the current idea being thrown around being micro-jumps of some kind. Of course, we don't want to lose the Frontier feel, but Frontier itself got around this problem by cheating like crazy, teleporting ships to where they were needed.
We also have a working script API, and there are plenty of missions available on the station bulletin boards. Scripts are written in Lua.