Um.... unless you are talking about a colony of people completely independent of earth (they never visit and get no materials from earth), you still have to take off from earth to get to the moon before taking off from the moon to get to....whereever.See this is the thing. Once we get to the moon and build a credible base there that is able to launch spacecraft, the amount of rocket fuel needed will go down drastically. You don't need to travel through an atmosphere and beat gravity on the moon. That is where all that rocket fuel goes. As soon as we get to the moon everything will become far easier because of that pesky thing known as atmosphere.
Fortunatly, all of our great-great-great-great-great grandchildren will be dead long before "forever". Meanwhile, I just got my January heating and electric bill.....We can't stay on earth forever, no matter how well we protect her.
Lets deal with real problems, not speculative fantasies about where we might need to be in 10,000 years.
Fortunatly, we don't have to kill people off, they die on their own after 75 years or so. We only have to slow the rate of having offspring....which is already happening. Most western countries are actually shrinking already (the US is an exception largely due to immigration).There will soon be overpopulation (there really already is) and the earth just won't hold everyone. We can't just start killing people off...
And in any case, I'm not sure what you think will happen if the population becomes 10x what it is today (unlikely in the next hundred or two years)....but whatever happens certainly won't be worth the quadrillions of dollars necessary to put major colonies on the moon and Mars. Better to spend that money on food!
We don't have to expand now (and I don't think we will ever - certainly it can't be predicted with any reliability when it might happen), so we don't need to start now. Again, I just got my energy bills for January - this is a now problem and we have enough "now" problems we need to deal with now....so we have to expand. Why not start now?
Huh? Well that's just gibberish. I've been joking (only half joking really...) about Star Trek, but that sounds like something straight out of the Star Trek universe, where money doesn't exist (except where it does exist ). You do realize that Gene Roddenberry was a sci fi writer, not an economist, scientist or political philosopher, right? I have a copy of the Star Trek technical manual on my bookshelf. Great read, but in the preface, they define the word technobabble. It's basically technical sounding words or phrases that are actually just meaningless. That's what you've posted here.Why should space exploration cost money? Why should money even matter? Shouldn't we put everything into this and go for the gold?