It should require anything more than the minimum standard hardware on any Mac currently being sold for 3 reasons, 1. Apple's computers aren't very customizable and it will need to run on any computer they sell at the release date, 2. there is hardly any chance for major changes in computer being sold by then, and 3. they would have to immediately pull the ad slamming Windows for it's relatively hefty hardware requirements for Vista.
That's just my guess. I don't think Apple would lay any special requirements on it's loyal customers. However, to get the full use of the 64 bit availability, you will need at least a C2D processor as far as I know.
EDIT: From the link:
You must have a Macintosh computer with:
an Intel processor or a PowerPC G4 or G5 processor
a DVD drive
at least 256 MB of RAM for a Power-PC based Mac and 512 MB for an Intel-based Mac (additional RAM is recommended for development purposes)
a built-in display or a display connected to an Apple-supplied video card supported by your computer
at least 6 GB of disk space available, or 8 GB if you install the developer tools
That seems pretty minimal, but sounds about right. Great find!!