I know that, like a said FFX HD was listed December 31, 2013, but the release was not definite. I was trying to say will the placeholder release date should be around that time (Like FFX HD which will be released on March)?
It'll have no relevance at all. Basically, nobody has a clue about when FFXV will come out. With FFX, we could make a decent enough estimate, but if they don't have a date, they'll always whack Dec 31st onto any game they don't know the date of. It was generally assumed FFX would come out in the first quarter of 2014 anyway, after not getting a date for so long.
With FFXV, Amazon giving a placeholder of Dec 31st bears no relevance at all to when FFXV might come out. Even if it did come out in Jan 2015, it wouldn't be because Amazon had the right estimate - it's simply the only placeholder date they can put on it for now, and would just be coincidence if it did come out not long after then.
I think most people here agree, though, that XV won't be out here until Summer 2015 at the
earliest (I'm expecting Q3 or Q4 2015 for us). And if Amazon later on changes their estimate to July 31st, 2015, it won't be because they think the same as us; it'll just be because that's the next logical placeholder to put down.