One answer or the answer?

Well, I may have found an answer to my question last week. I did a little research on "sustainability" and what it stands for. It is basically and very shortened a principle of preserving resources for future generations so they will have a choice. It is based on ecological sustainability but streams of economic and social sustainability are separately researched. A sustainable system or process will last indefinitely. The most significant definition is the one of the Brundtland-Commission found on wikipedia: 

"One of the first and most oft-cited definitions of sustainability, and almost certainly the one that will survive for posterity, is the one created by the Brundtland Commission, led by the former Norwegian Prime Minister Gro Harlem Brundtland. The Commission defined sustainable development as development that "meets the needs of the present without compromising the ability of future generations to meet their own needs."^[1] The Brundtland definition thus implicitly argues for the rights of future generations to raw materials and vital ecosystem services to be taken into account in decision making." (wikipedia.com)

It makes a lot sense actually. But when you look at the real world it is hardly seen. The question remaining is: why should we care what happens in the future? Why no being egoistic? And is it possible that future generations will adapt to their environment and find ways to live anyway?  Is sustainable politics just another ideology? Let the strongest survive!? I don´t know tell me!