The conference will come a week before the Tokyo Game Show, where Nintendo typically does not exhibit but does use for media briefings. The Wii, for example, was introduced at the 2005 TGS.
Nintendo was recently slammed by critics for an underwhelming showing at E3 2008. Nintendo apologized shortly after the conference and promised that 'core' games are on the way. The Fall Conference may play host to some announcements fulfilling that promise.
Today's announcement of pending announcements comes from the Japanese Nihon Securities Journal, which was spotted and translated by Kotaku.