A religion that becomes a world religion is not going to stay the same. Compare early Christianity with modern Christianity, or basically any religion with what it has become today. For the most part, forcing a religion to stay the same would mean that it cannot change when needed, so would be unable to meet the needs of various groups of people.
That said, maybe there is a way to get it spread more in India. If it becomes widespread, there could be a much more significant number in India, with luck up to 500,000,000.