Is 'Living Building' The Future of Cities?

A new six story "living building" is being constructed in downtown Seattle, set to revolutionize what we think of sustainable architecture. The building is said to take in as much water and electricity as it consumes making it the cleanest building out there...but is it worth it? Designers say yes. Despite it costing  a third more than the average office building, they've designed the building to last 250 years as compared to a normal buildings life expectancy of around 40.

Will it work? Is it practical? Do we tear down other buildings now or later? Who knows. I think we need to tackle the issue of making current buildings more efficient (it can't be good for the environment to scrap a building's worth of supplies just to build a new, green one...with another building's worth of supplies), but I think it's good we are at least seriously looking into it.
http://usnews.msnbc.msn.com/_news/2012/03/20/10226909-could-this-30-million-green-tower-be-the-future-of-world-cities