There's a lot of talk about Indian be the greatest superpower, but realistically will Indians be content with being in 3rd place?
Even making it to 3rd place is quite an accomplishment, that means beating out nations like Japan, Germany, Brazil, Mexico, Saudi Arabia, Indonesia, (united?) Korea, UK, France, Russia, South Africa, Egypt.
Imagine India's economic might greater than Japan, military might greater than Russia. And do you really think in less than 20 years India's science & technology will surpass Japan+Germany+Russia's???
I'm only being honest and realistic. Making it to 3rd place means accomplishing all this. Let's not forget while India is advancing all those nations I mention will not sit at home picking their noses while watching on their 100+inch OLED TVs'. They are working just as hard (or even harder) to keep their positions (or advance).
Who will be at the top depends on a lot of facts and the COMBINED efforts of all its citizens. Overall, I do believe it is 'possible' for India to be in 3rd place within 3 decades --- Indians have the dream and drive.
As the fellow said earlier, let's continue this discussion in 30 years. Meanwhile all actions from now till then will help in determining the outcome! Good luck!