Nobody will deny them their right to do so. But parents will in the future have no right to do only this, given that raising their children only into their own nation is totalitarian and even constitutes a major form of brainwashing. Of the parents of tomorrow, we would expect not only that they do the task of handing over their own culture and language, but also that they open the windows and doors to other cultures and languages. Not with the help of movies, travel, TV, and immigrants. To be multiglot or polyglot is not only possible, it is even simple in a world where nations increasingly intermarry and live around each other.
Children pick up languages easily.
They have a very high capacity for learning and mastering languages with no clear upper limit. Languages flow along the bonding, making learning from significant others easier than school learning, except when there is bonding with the teacher or classmates of that language. The language is part of that person. Learning becomes a question of tuning in to the right person for the right language, until you master the tongue and can converse freely with anybody. Each significant other should speak only one language to the child.