"Productivity growth will help India sustain over 8% growth until 2020 and become the second largest economy in the world, ahead of the US, by 2050, Goldman Sachs has said, scaling up estimates of the country's prospects in its October 2003 research paper widely known as the BRICs report."
The nations with the largest economies would then be China, India, and the U.S. in that order.
I'll have more to say about this in an upcoming post. Meanwhile, the blog A Wide Angle View of India offers a summary of the updated Goldman Sachs report.