As for the subject I personally do not think they will port XIII over to any other console. Simply because its physically not possible due to the WHITE engines requirements.
The White Engine is apparently open platform, thus could be ported to the 360 fairly easily.

http://au.gamespot.com/news/6167571.html
HS: I feel that the Final Fantasy series should come to Xbox 360 as well. This is wise. It makes so much sense to me...it has so much potential in North America and in Europe. So there's a great chance for the series to succeed on 360 as well.
[in English] And I heard they made the White Engine open platform as well.