With English as the current lingua franca, I think it's nearly
impossible for Chinese(Mandarin) or Tamil to replace English as the
main language. But when the time China and India had matured, maybe
Mandarin will take the 2nd place as in the business language, and I
don't think Tamil will ever be in the business language. Seeing the
Mandarin are widely used, as the 2nd most widely used language in the
world (if I'm not mistaken), and the usage of the language for current
business world, especially in Chinese oriented countries and Malaysia.
This usage might be the pusher for it to become the 2nd business
language.