What is the citizenship of an Indian child born in the United States?

A friend of mine is expecting a baby this December. He had few doubts about the citizenship of his child.
He and his wife are Indian Citizens born in India. Both his and her parents are Indian Citizens by birth. They hold valid Indian Passports.
They have been residing in the US for past 3 years and the child will be born in the United States.
So the child by the virtue of lex soli be a citizen of the US
Also the child by the virtue of lex sanguinis be a citizen of India
my question is when the parents register the childs birth at an Indian Mission, the child gets his Indian Citizenship. But the application requires both the parents to declare that the child has not accquired another citizenship. Will this declaration be true?
If so, will the child loose his US Citizenship?
What happens when the child becomes a major. Will he be required to denounce one of his citizenship?
What happens if the parents become a naturalized US Citizen in the future?