I think it is both. I can easily see coming up with a Korean Civ and simultaneously coming up with a Korean localization to try and capitalize on the attraction that new Civ might have in its geographical market. I don't know if that synergy will actually get them much of anywhere, but it sounds like the kind of thing a marketing committee could convince itself of.
Next they could do an English language localization so I don't see such grammatical boners as "a The Pyramids", "Lord Elizabeth" and "The Incas is". I figure if they're so careful to follow other language conventions by creating localization, they ought to be able to do the same thing for English. They may need two versions, English English and American English, but it is still doable ar at least something a picky Civ fanatic could hope for.