I've been checking a wikia of Final Fantasy for information of Dissidia. And it says it will be mid-year of 2009 in the United States. I roughly guess either June or July, somewhere in-between those months.
Wiki is a terrible source of information, especially when it comes to release dates. If we're lucky, yeh, maybe June or July. But I doubt that.
We have know that since they said mid-year...Also it might be released on the day which the first Final Fantasy was released here.
Some playstation magasigns (even though they don't know what their tslking about) guess that the game will reach England by summer or September so probibly would be July for America.
Um, they had a press release about this on the official NA SE site. http://release.square-enix.com/na/2008/12/dissidia_final_fantasy_announced_for_mid-year_2009.html And I think that this might not be delayed either, considering them also working on the English versions for 358 days.