A video recently featured in the Daily Mail examining where 1 billion more people could fit on earth:
Although the video has a somewhat negative tone, it is clear to me from the maps used that at least two continents’ worth of land is able to fit many more people. The demographers I have read indicate that a mass population drop is expected to occur by mid-century and beyond due to suicidal level birthrates in most nations worldwide.* Japan is one such nation, although interestingly enough the video does not feature it as a place where more people could settle in the future. I expect that once the “Great Die-Off” gets underway, the tone of videos like this will dramatically change.
*Deagel’s predictions are also interesting to study in this regard: http://www.deagel.com/country/forecast.aspx