The HD Final Fantasy Type-0 ESRB rating will be M for mature, according to the Jump Festa trailer:
And I can tell you that what you see in the trailer isn’t the darkest content.
It appears Square Enix, while unwilling to pay record company Toys Factory for international use of “Zero” by Bump of Chicken for merely a PSP game, is indeed OK shelling out the fees for a home console release (a factor in the decision not to localize). Another sad case of Sony’s handhelds getting shafted, I suppose. Anyway, you can hear the song playing in the background during most of the trailer, as sung by Bump of Chicken. In the beginning part, that’s cast member Ace singing it.
Might seem kinda jarring for Ace to switch from English to Japanese during gameplay like that (he sings the song twice during the game), but it looks like that’s what’s happening.