Looking back, every Nintendo hardware release in the United States since the GameCube were released on a Sunday:
DS Lite - June 11th, 2006
GameBoy Micro - Oct. 2nd, 2005
DS - Nov. 21st, 2004
GameBoy Adv. SP - Mar. 23rd, 2003
GameCube - Nov. 18th, 2001
Keeping that in mind, while I think it's possible that the Wii launch could be in October, I find it unlikely. If it is in October, it'll be at the very end, probably October 29th. A much more likely scenerio seems like a November 5th or 12th launch.