Never change a winning team. Everyone nowadays is taught English in school. That does not mean that other languages will perish. On the contrary, I think if we try to put restrictions on one dominant language, or the use of it, the language we actually set out to protect will disintegrate and perish. If you do not let the smaller languages, like Danish, develop in the world in which we exist in today, it will lose its meaning. Small languages like Danish or Slovak have survived because they manage to interact with languages from surrounding countries and world or regional dominant powers. If you try to prevent that, the language will lose its relevance.
Mastering (more or less) two languages is twice as good as mastering one, so I only see benefits for those from smaller nations like Slovakia.
Jesper, Denmark