The november issue of Game Informer featured an article on Advent Children.
It said that FF7 will be re-released on the PS2 and will come with the Advent Children DVD.
The last paragraph stated:
"Square Enixhasn't set a firm release date just yet, but is hoping for summer 2004 in Japan. The U.S. release will follow shortly thereafter."

so it will be released about the same time as the Naruto movie.