What does it have to do with India bashing? Take off your ultra-nationalist glasses and accept the harsh realities buddy. India has a long way to reach China (forget USA). The above was not even my guess, it is from Goldman Sachs.
Though i accept that PPP is a more accurate measure. If we take into account India's PPP growth the estimation will differ greatly. I haven't found any sources on future estimation of PPP for India, but we can calculate the difference today and go from there. Today India's GDP per capita is $1,527 and PPP per capita is $3,703. Roughly we can say that when converted to PPP the difference is almost double. Hence, a rough estimation of Indias PPP per capita in 2030 will be around 10.000 (Since GDP was estimated as 4.500 by Goldman Sachs for 2030). Therefore i don't think India can become an economic superpower by 2030. Instead you guys should focus on raising India's standards.