http://www.theatlantic.com/business/archive/2012/02/the-world-in-2050-when-the-5-largest-economies-are-the-brics-and-us/253160/
http://business.blogs.cnn.com/2012/01/12/worlds-top-economies-in-2050-will-be/
http://www.theguardian.com/global-development/datablog/2012/nov/09/developing-economies-overtake-west-2050-oecd-forecasts
Books about the decline of American hegemony and rise of the BRICs:
http://www.amazon.com/World-Out-Balance-International-Relations/dp/0691137846/ref=sr_1_1?ie=UTF8&qid=1396056968&sr=8-1&keywords=world+out+of+balance
http://www.amazon.com/No-Ones-World-Council-Relations/dp/0199325227/ref=sr_1_1?s=books&ie=UTF8&qid=1396056994&sr=1-1&keywords=no+ones+world