Nintendo has released a late 2009/2010 release list of first party titles and the manner in which Golden Sun is listed gives hope for a 2009 release in Japan.
The game is listed alongside The Legend of Zelda: Spirit Tracks as "TBA" for a Japanese release - but interestingly Spirit Tracks is a confirmed Holiday 2009 release in the USA.
With Spirit Tracks dated to hit America before Christmas it's likely it will also land in Japan before the end of the year - and one that only leaves one other "TBA" game on the list - Golden Sun.
Perhaps that will do the same?