I've done business in both China and India. At the table we all speak English. All of the correspondence, minutes, and contracts are presented in English first. Their schools teach English as a second language at all levels for the purpose of preparing their population to be members of a global community.
International court proceedings are conducted in English.
The world's un-official language is English, both in highest use by population and by territory.
And per my original statement should the Earth ever agree to a planetary standard language, which is not saying that it will be so, it would most likely be in the interests of business and law and thus that language would be English.