In all fairness i think this is one more evidence FFVII is definatly coming out. Sony knows there's huge business in FFVII, see spin-offs and movie(s), check sales on FFVII - PS1, check the huge fanbase that is ever growing.
If you'd ask anyone who wants a ps3 for a certain game, there's only one answer to it: FFVII. There are hints left by Square Enix in the secret ending of the psp game: FF Crisis Core. "The story will be continued in FFVII...." was the message they send us. Not only did they suprise us with the secret ending, they used the E3 2005 PS3 footage for it, which suggests the viewer the story will be continued in breath-taking new graphics version of FFVII.
If you ask me why on earth FFXIII goes multiplatform, i think it wouldn't be a strange train of thought if you would have known a FFVII remake is on its way and it will be exclusive. Will FFXIII be a huge loss to the PS3 owners then?
There are lots of Square-Enix employees that joined the company because they were inspired by FFVII and wanted to be involved in future FF-related games, and even hoped to be involved in a remake someday. (read this in an interview somewhere)
Why keep things quiet? A remake of a legendary game ain't the easiest task one can do. What you need is time, lots of time. The wait seems less for us all who have been waiting for this game if they would announce it when the game is finished or almost finished. Rather than telling us about the remake in 2005 and the release date is in 2009/2010. The good side about keeping things quiet is that the game is so popular, (and so is its ps3 tech trailer) that the rumour is a free marketing tool. Plus it won't put any ps3 games in the 'shadow' aslong as the remake isn't officialy acknowledged yet.
Imagine us knowing FFVII is going to be released. Would anyone look forward to another game then? Not as much i think..
Ah well, that was my train of thought. Sorry for the long story. :)