The '5' is of course intentional.
The theory that it's 5 new products is interesting but I believe the stronger guess is that it will be a reference to the iPhone 5 as the name of the next phone.
(Can we please drop the nerd counter that it's the sixth-gen iPhone. The average consumer doesn't know this and more importantly, doesn't care.)
Question: Why would Apple drop the number from the iPad but keep it with the iPhone???
I don't think Apple will officially market it as iPhone 5. But it has received a lot of media attention by that name. It is no secret that the iPhone 5 will most likely be introduced during this event.
Alternatively, maybe the 5 refers to another date for the iPad mini unveiling, who knows.
One thing I am absolutely sure of is that on 9/12 I will be reloading the Apple store page, until it is updated, after which I will order 2 new iPhone