Interesting point about "one language". With a "universal translator" type device I'd imagine that different languages will thrive rather than stagnate. Speaking one's language would become a source of pride, a part of cultural identity. A language already is that to a great extent (see Quebec and the French language rules) and I think that this kind of device would only increase that kind of stuff. The machine would do the work allowing for the "purity" of the language to remain.

Very cool and some interesting social ramifications are possible.