OK, now take a look at its nominal GDP: $3.42 trillion. Read up on PPP mate. It can be an effective tool to use, but trying to use it to 'prove' that a country is going to be a dominant economic superpower in 40 years time is fairly meaningless - about as meaningless as using, say, GDP per capita. Nominal GDP isn't even a good indicator of that, tbh, but at least nominal is a half-decent ranking of a country's economy on the international scale.
But yeah, India is lagging behind a bit at the moment. Its stable democracy, political freedom, relatively low income disparity, along with much of the same economic growth power as China, would indicate it is the more likely candidate for 'future superpower'.
Anyway, if you were trying to prove a point, you didn't; China hasn't overtaken anybody. I'm sure that its economy will continue to grow, but so will America's, and so will India's. China isn't going to bloom forever; such growth tends to be more like logistic than exponential.
I have far more faith in a prediction about India or Brazil's future than I do China's; it's far too volatile and unstable. And I mean, forgive me for being cynical, but considering how often the Chinese government fabricates things, I wouldn't be very surprised if its own GDP is reported with a skew by the Chinese Bureau of Statistics.