Yeah very true. All the developed countries have low birth rates, some are even negative like Japan. 

I think the population has exploded as we've been able to expand our technologies that correlated with our developement and exploitation of fossil fuels. If new technologies can't keep up with the depletion of fossil fuels the population wil contract. Less developed nations will feel the pinch first as is always the case.

Earth will never be over populated, cities yes but not earth. Even with cities, ww3 is on our heels, and I'm expecting 1 billion dead people when it's all said and done, so even cities will eventually be depopulated.

Well when I'd say 100-300 years. Obviously the earth is already over populated and in a position where it can't sustain the population indefinitly but it isn't yet at the point where the population can't be supported at least for the time being.

Example if the consumption of America was reduced to that of the rest of the world not even talking third world just say Canada (Which is already a major consumer) the rest of the world would be raised drastically if that consumption was shared. If the west and the first world reduced its consumption and instead shared its wealth and food the third world could all be fed and clothed etc...etc...

But right now China's consumption is growing despite a smaller population. They expect China to be consuming as much as America in not to long as their economy grows they expect to live the American life style. The American life style is unsustainable and we can't afford a second country consuming the amount that the US does.

I'd suspect that America and China will do everything in their power to maintain (America) and gain (China) the American life style the US currently enjoys. As they do they will starve the rest of the world of resources needed to maintain their populations. As these resources run out the poorer countries will start fighting more and more over the little resources left, America and China will intervene in these conflicts as much as possible to gain vital resources to maintain the life styles their countrymen expect. After a while other countries like Russia will begin feeling more and more poor and will also start fighting for what remains of the resources.

Pretty soon the military powers of the world will be getting desperate to maintain their countries life styles. As those life styles become impossible to maintain the countries will try to preserve as much as possible. Soon we will see escalations and likely a North American currency to protect the resources in North America, Canada will quickly be milked for everything its worth by Nato. If America remains in the Nato alliance then the alliance will likely move to protect its populations interests resorting in massive conflicts.

In the end the third world will die off almost entirely as the first world sucks it dry. War, famine and lack of resources will lead to wide spread death like we have never seen before. I still think the world powers will try to avoid using nukes, meaning the nuclear powers will likely try to avoid clashes on each others soil.

Unfortunetly for the world once the third world is sucked dry the second world will follow and then one by one the first world countries will be fully third world before they too collapse. Anarchy and chaos will ensue and the countries that fought so hard to maintain control and those life styles will implode.I'm guessing the US will try to preserve itself till this point, the rich 1% will be taking care of the rest of the population to a degree to try and maintain the life styles of the American people. If the wealthy do not and the welfare rates grow to large and the poor become to angry the US will implode prematurely and the world will eat it alive.

In the end 300 years from now I don't expect any of our countries to be in the same condition they are now. The Governments will have all collapsed or been splintered to the point they don't control much of the countries they are now. A one world Government will be put in place during this chaos as an attempt to save the globe but it will not work.

In the end we will go back to the way we were before the industrial revolution. Every town and city for themselves essentially, regional alliances being used to keep the people alive. 90% of the worlds population will be wiped out and the world will essentially begin a new if you don't believe in Biblical prophecy.

I really don't think man kind will be wiped out entirely for another few thousand years if God doesn't come back (As Christians believe).

Irrelevant question.

For the last fifty years man's birthrate has at least halved. Soon it will be under 2 children per woman.

The biggest problem for man's future is the aging population, not the birthrate.

Never by population growth.

If there are ever too many people to support.

Those people will die... and everything will be "fine".