If the concept itself doesn't exist in a language, good luck with that universal translator.
Well, English copes easily enough by simply assimilating, and if need be, adjusting. There's no need to translate schadenfreude or ombudsman or blunderbuss, let alone learn German or Swedish or Dutch in order to get the translation, as long as you learn that this new English word has this certain meaning. This counts as "learning English", not as "translating".
The UT automates even that process by inventing words like "troglyte" for the user and letting him slowly catch on.
Do languages undergo revival? It appears that they simply die out one by one, until presumably only one is left (and with something like the UT, perhaps none). Except of course as hobby projects for an insignificant minority; there is always an insignificant minority available for X regardless of the value of X.