Free for two weeks
Lighting Returns: Final Fantasy XIII may have launched in Japan today, but it'll hit other markets on Valentine's Day, February 14th. When it finally does come overseas, you'll have the opportunity to download a Japanese voice-over pack as DLC -- it's free for two weeks, then it reverts into paid content.
I know people often say that they don't care if games have dual-audio or not given that it's pretty expensive to put in, but I for one appreciate the option. As always, even if you're not planning on picking up the game at launch, download the DLC for free just in case, as it'll be waiting whenever you get around to it.