I agree with you, and thaumaturgy below — it’s clear that they signed a 5-year agreement. But as Engadget notes in your first reference, contracts can be canceled, amended, and breached in many ways, and the two companies have had a number of chances to renegotiate over the last three years, including when:

- Apple adopted subsidized pricing soon after the first iPhone was released (to sell it at $399/8GB instead of $599)

- AT&T’s serviced proved spotty and unreliable for many at times

- the iPad was introduced with an optional AT&T 3G data plan

So it’s hard to know if the agreement is still in place, or if it means enough to prevent Apple from pursuing the large Verizon customer base.

You might be right. At the very least, the exclusivity does seem to officially still be in effect; looks like I got caught up in some speculations earlier this year. On the other hand, AT&T certainly is preparing for the loss of exclusivity [1], and we know that AT&T picked up exclusivity for the iPad, so it would make sense that they were opting to drop the iPhone deal while picking up the iPad (which is also what an AT&T insider that I know was saying quite a while back).

[1]: http://www.intomobile.com/2010/09/21/att-iphone-exclusivity/