It's all hypothetical really, because none of us "really" knows what will happen. It is more like an educated guess. My position could be considered "dramatic" or "extreme"
But what I do know is that we are already seeing the effects of pollution. Cancer and other diseases are just the norm now. It is a product of our environment and our consumption and lifestyle. We are evolving in our own way. Life does adapt as long as it can. But we may have to live as sick people, and our quality of life may suffer. But as for the dramatic version it could happen. None of us really knows what exactly will be the consequences of our actions.
You are correct most people don't have an interest in destroying the earth with pollution. Even the mega corporations are not looking that far ahead I am sure. Money is the bottom line and they are not able to see past today nor do some of them care to. They are in it for the moment. I am sure the goal is not to cause destruction but sadly in many of the cases that is the outcome. It is the consequence of the action. Even if not intended. I think most people "common plebians" would not want to participate in global pollution and would choose alternatives if presented or available. Life is hard and people take the path of least resistance.
Ah Yellowstone. I was really just arguing a point there. My bad. Perhaps there would not be complete extinction you are correct there. But it is possible that it could cause and ice age and I am not really sure what all would go down with that. I am not sure anyone really knows what would happen.
What I do know is that this topic is no longer something that only the future generations need to worry about it is affecting us as we speak. We are now living in the world that has become more toxic, and we are suffering the consequences. If we are suffering this now with the way things are as they are, then how much more so will we suffer when regulations are wiped away, and accidents become the norm. The things we face now are already great, and more than we can handle, how will we handle another fukushima, or BP? There are many more to come. In china people already buy air, its already happening. It is sad really.