Well, now the event seems to have moved to October 23... but it's reportedly for the iPad mini, and no further word on the retina 13-inch MacBook Pro.
Don't rule out the possibility of Tim Cook pulling a 'one last thing' at the end of the keynote on the 23rd.
I don't see a retina 13" being a front liner or having it's own keynote like the first retina 15" was, but I see it drawing a lot of oohs and aahs at the tail end of another event.