More then likely, DVD9 isn't enough. Take a look at Squenix's history and overall they tend to lean towards non linear titles for their main RPGs(all told you have fourteen of their nineteen main series beign non linear) and they tend to not rely on reused assets very much as BethSoft did for Oblivion. The 360 was never a viable option at all, I don't know why anyone would think it would be. The other two systems that had a chance at landing the title, the PS2 and Wii, were both also DVD9 limited. From a business perspective in the time frame that the game will come out it makes by far the most sense to release it on the PS2, their sales would likely be much higher then they would be on either of the other two options, but it wouldn't allow them to release the game in the way that they want to do it.
I don't think this is a slam in the least on the 360. The 360 sold 0.4% of what the DS sold this week- it is not a viable platform for the Japanese market. MS made their choices, and of those choices was the choice to go with DVD9 which everyone knew was going to be an issue if they wanted to land certain JRPG series on their systems(FF being the highest profile in the US). They decided to focus their hardware on the US and European market and so far that seems to be going the way they want it to(they have Gears of War which will likely sell better then FF in either of the two territories they are focusing on).