I genuinely think that a Lunar base is quite do-able and it's only about 3 days to get there. SpaceX and NASA have the budget and intent to do it (more or less), South lunar pole is good destination for reasons of water ice there and also .... FAR less extreme periods of daylight and darkness (hope everyone realizes that in many places on the moon it is 14days of searing sunlight and then 14 days of utter blackness... = very difficult to manage temperature extremes, sufficient solar power, etc etc).
Mars is probably visitable (in 10 to 15yrs) but in my opinion (sorry Elon) there won't be a colony of more than 20 or 30 people. It's simply too hard to LEAVE Mars and return to earth due to fuel issues. So unless people sign up for a one-way trip (and they might well do that) , colonizing Mars is incredibly f'ing hard. Sabbatier process takes massive 300 to 400C temperatures, so that's v v difficult in itself.
Plus ....opportunity to travel to Mars is just once every 2yrs-ish (when the planets are close enough)
Europa (moon of Jupiter) is simply very far away and massive radiation given off from Jupiter but quite promising for existing ocean aquatic life.
Titan is interesting, moon of Saturn. Europa Clipper mission is launching soon on a Falcon Heavy ( year or two I think) and that's a planetary probe heading to Europa.
As for interstellar travel....forget chemical rocket propulsion for that --- gonna need nuclear thermal drive or an ion drive or something we haven't yet thought of. Even at 10% the speed of light (which is incredibly f'ing fast (67million mph) and probably not do-able even with some amazing propulsion system), it'd take decades to reach close stars (40yrs+ to Alpha Centauri even if we ignore accel and decel times) and so..... nope in my view interstellar travel just never happening. Mankind will end itself via killing hte planet in a few hundred years.
