If you've read Blood Music or Prey, you may find this somewhat disturbing, but it seems that tests of the TETwalker robot have gone well enough that NASA will be proceeding with miniaturizing them. Really really tiny.
These miniature TETwalkers, when joined together in "swarms," will have great advantages over current systems. The swarm has abundant flexibility so it can change its shape to accomplish highly diverse goals. For example, while traveling through a planet's atmosphere, the swarm might flatten itself to form an aerodynamic shield. Upon landing, it can shift its shape to form a snake-like swarm and slither away over difficult terrain. If it finds something interesting, it can grow an antenna and transmit data to Earth. Highly-collapsible material can also be strung between nodes for temperature control or to create a deployable solar sail.
So the robots swarm together to form ANTS, which scientists hope to send to Mars by 2034. It's promising technology, but just a bit frightening.