Another user posted an article[1] where an analyst suggested 10 million, with a "worst-case scenario" of 6 million. Obviously, no-one has any idea what Apple's target/expectations were.

In any case, I didn't say that 5 million devices wasn't impressive. It is. But it isn't necessarily evidence that the iPhone 5 is earth-shatteringly great, it's just good enough for people to upgrade.

[1] http://articles.cnn.com/2012-09-19/tech/tech_mobile_iphone-5...