Looks like we were wrong! It still doesn't really make sense, but leaked search results directly from Apple.com all but confirm that the New iPhone will be named the iPhone 5.
First pointed out by 9to5Mac, the internal disclosure is easy to reproduce on your own. Just type "iPhone 5" into Apple's own website search, and links to unpublished PR documents announcing the glory of the new handset come right up. The links don't work, but the URLs say it all: dated September 2012 (that's now!), "Apple Introduces iPhone 5." [9to5Mac]
Update: A search for "new-ipod" yields the following (also unreleased) PR dispatch regarding a new iPod Touch and Nano. Looks like the phone won't be the only show today.
Update 2: Looks like we'll be getting iTunes 11 today as well.
Update 3: Hey look, the iPhone 5 will have LTE.