The next tower will probably be built for a legitimate reason, Malte. The USA actually has an economy that can fill a tower of that size with real businesses and jobs. Germany, Japan, China, France, even Canada have real economies with real production and a serious reason to build such a thing. No offense meant to the Canadians.
Dubai was a place for rich people to invest in properties, expecting unrealistic returns, and hoping that prices would keep going up forever. It didn't work. Speculation and construction are not the same things as real production.
And yes, helping the environment is a more noble cause. I agree.