"During coffee breaks, the Pope meets with the synod's working groups, which are divided by languages. In past days he spoke with members of the French-speaking groups, and today he spoke with the Spanish-speaking groups."
If they all spoke Latin, there wouldn't be any need to split up like that.
As for Latin, a common language would be good to bring all the bishops of the world together. More important still, we need to bring back the common theology that was taught when Latin reigned in the seminaries and universities.
Maybe I am wrong, but I heard that even at Vatican I many bishops had a hard time communicating orally in Latin. In the 19th Century the usuall means was French.