I don't know that Mars is the limit for human space exploration, but it likely is our limit for planetary body colonization given that it's the farthest rocky body planet from the sun capable of being terraformed (within our solar system). Gas giants' moons are small and inhospitable with lots of radiation. It wouldn't make much sense to set up a permanent base there -- or even on an asteroid for that matter. Why would any astronaut even want to visit in person when they can send a probe instead?
I don't think using NEVER is hubris. We can never travel faster than the speed of light due to the fundamental laws of the universe. Wormholes and warp drives are fictional, fantasy ideas that require exotic matter or control over undiscovered gravitons to work. Exotic matter likely does not exist (it's possible gravitons don't exist either), and there's no known way to focus gravitons as they don't interact via other fundamental forces, so FTL travel will likely NEVER happen. FTL travel can also create paradoxes, which is why many conclude it's impossible.
So, without FTL travel, it would take many lifetimes to reach another habitable planet to terraform. Assuming we had the technology to do it, why would the human race choose to endure several lifetimes on a ship with scarce resources and constant peril from radiation and destruction only to hurtle towards some destination that could also end in disaster? I imagine if our sun went red giant, we might decide to move on if Mars were no longer hospitable. Perhaps by then, we could simply seed a new planet with stored genetic material and grow new humans at the destination after terraforming instead of sending live humans on the journey. Any living human would be unlikely to survive the journey anyway -- even if we advanced cryonic suspension / hypersleep substantially.
I think it's hubris to assume "almost anything his possible given another 2000 years" -- wow. Talk about hubris in the faith of what mankind can do. I mean, we understand so much more about the universe now than 200 years ago, but that's the problem. We discovered laws of mechanical motion and electricity/magnetism and exploited them to the fullest. We don't have any new laws or forces to exploit anymore. We only need to figure out dark matter, dark energy, and a unified field theory (assuming one exists.. possibly through string theory) and we're done. No more magic to discover. No more undiscovered laws of nature to exploit for future technologies. Our last big life-changing discovery (other than the higgs boson and meta materials) was superconductors over 100 years ago.
We still have a lot to learn, no doubt -- especially in biology and nano-tech, but no new fundamentals to discover.
Have a look at when some of our "modern" tech came about. Today, we're mostly miniaturizing, combining, and refining tech that we invented many decades if not centuries ago. Until some new fundamental forces pop out of the LHC for physicists to exploit, there will be no FTL drives. Unfortunately, the standard model of particle physics doesn't lend itself to there being any other forces, and the higgs boson was the last missing piece of the puzzle save for perhaps the graviton.
Steam Locomotive - 1804
Telephones - 1876
Incandescent Light Bulbs - 1879
Automobiles - 1885
X-ray machine - 1890
Airplanes - 1903
Television - 1925
Computers - 1822 mechanical, 1946 electrical
Microwave Oven - 1946
LEDs - 1962
Saturn V rocket (moon launch) -- 1969
MRI - 1977
internet - 1982 (with research started as early as 1960 and various government implementations internally used)