Economic rent like this pops up even in human-made domains of potentially infinite expanse, such as the internet. There is no limit to the number of domain names which may exist yet some are far more valuable than those which can be claimed for low-to-no cost. Even social media platforms are valued to include the economic rent of their own user communities. For example, even if there came along a social media platform which was better than Facebook in every way, users would still value Facebook more because it has more community and community-generated activity and content.
Same with domain names. People are interested in using shorter domains like abc.com, not long ones such as xyajfbeusnfdbdjak.craptld
The scarcity applies to a grade of land or string, not to all land in the Universe or string space in total.
It is difficult to compare the 'grades' of land, because the grading is not discrete but somewhat continuous.
The hypothetical expansion of the human race in the coming centuries has no bearing on decisions that are made with the next years and decades in mind.
Labor is in theory infinitely expandable. Capital is infinitely expandable. Land (and natural opportunities) is fixed in supply, so according to Georgists there is no moral argument for favoring somebody for its monopolization. It should be community owned and rights of use to it should be given out to people, priced by a market mechanism.
Labor and capital don't suffer from fixed supply or renewability so according to Georgists there is no need to prevent it from expanding, eg. by slapping taxes on it.
Georgist movement is also known as single-tax or zero-tax movement, because they advocate that there should be no taxes on labor, consumption or capital. The only tax implemented should be the natural monopoly tax (land value tax). They say it would be enough to finace government from it because there are crazy trillions of dollars parked in real estate. Real estate price is actually land value price (location, location, lovation), so only land tax would suffice and there is no need for property taxation, which is actually product of someone's labor.
Some Georgists say that Land Value Tax is not even a tax but a payment for exclusive rights of use. You pay for the service the government gives you directly, therefore it's not a tax. In this way they argue you can run a society with exactly ZERO taxes and paradoxically raise even more money than current tax system.