http://en.wikipedia.org/wiki/Demographic_transition
There goes the overpopulation theory.
The rest of your post is a slippery slope to me. And I'm not even saying that you're basically unable to properly assess what will happen in 200 years, and how the world will be in one century. How can you doubt so much then ? The problems in 2112 are most likely to be so different from today that you can't even imagine the form they could take.
You see, if you read properly the other posts I made for the debate. I never said this outcome was impossible, I said it was one of the least probable ones compared to other ways the world could become.
It's all a question of probability, and making an appeal to probability in this debate is basically neglecting all of the other possibilities in the name of a psychological bias, and getting definitely obsessed about an unsure truth.
In fact, of course you can't be sure of the course of history, what I said is that it's irrational to believe things that are less likely to happen than other things that are more likely to happen for the reasons I said. That's the point of this speculative debate.
I'm posting there just because I saw some people being wrongfully certain of some outcomes, and being certain of things when their probability to happen is lower than other possibilities unsettles me a little.
Yes nothing is sure, yet it isn't a reason to surrender to fantasms, because there is at least some sense to make there, and this is important. Stop getting obsessed about getting a certitude when you can't bring solid foundations to your thinking, I think an optimistic scepticism is the sanest opinion to have here.