Yeah, for all intents and purposes, with out a radical change in how space travel is thought of, it seems like we're pretty much stuck in this solar system. With terraforming techniques we could live on Venus and Mars too, but I can't even imagine what it would take to make Saturn or Jupiter habitable. Can you imagine how much space there is in this system though when compared to just Earth?
i know in theory everything is possible, but i doubt you could change the atmosphere of an entire planet, especially venus which is around a constant 300°C due to the greenhouse gases. we simply don't possess the resources to change an entire planets atmosphere, or at least to make it inhabitable.
i once saw a very interesting documentary about how we'd survive as a species when the sun begins its red giant phase and overheats the earth. first we'd move to mars, at which point would have similar temperatures to earth due to the suns increased size. we could inhabit that for a few hundred to a thousand years, depending on how rapid the suns size increases.
after mars there is no other inhabitable planet in the solar system, there are moons though. theres a moon just off jupiter which is covered in mile thick ice. by the time we'd need to colonize it the ice should have liquidized into one huge ocean. the idea was to set up dome colonies on the sea bed, by that time we should have developed the technology to do so.
i still can't see any hope of ever exploring outside of the solar system though. once a craft runs out of fuel, you can rely on momentum from planets gravitational pull, but after you get to the last planet of the solar system your pretty much stuck. it would really depend on if we can figure out nuclear fusion, which theoretically would tremendously increase energy outputs.