for those of you who are not complete nerds, Apple is notorious for a couple of things, including being very very secretive about product updates and introductions and for being dramatically nonchalant regarding said announcements when they come.
steve (jobs) has previously made major announcments (well, major for apple anyway) following long keynote speeches; he often ends his talk, but stops short of leaving the stage, saying, "one more thing..."
variations on this technique have been used for in so many launches that it is almost expected at this point, which apple is evidently having some fun with.
invitations came out today for an apple event on october 12, 1 later than Shawn's prediction. itunes 5 and the nano came out less than a month ago, so i doubt it has much, if anything, to do with ipod/itunes, which leaves the prospect of changes to apples, you know, <b>computers</b>.