It's what we thought... until the Wall Street Journal told us we were wrong. It's what USA Today originally reported, although nobody else was ever able to confirm it... until now. Nilay Patel at Engadget has unearthed some 2008 filings in a 2007 class-action lawsuit that clarify the matter: the AT&T/Apple deal for exclusive domestic service on the iPhone, which has caused much wailing and gnashing of teeth, was originally set for a five-year term. That would put the earliest appearance of a Verizon iPhone into the summer of 2012 -- assuming that there wasn't any reason for one or the other party to break off the agreement.
Those disclosures are a couple of years old now, and the circumstances may have changed a bit (exclusivity may have been extended since then), but at least there's some grounding for what the original half-decade setup was intended to be. Even though recent analyst musings led to the surmise that the iPad's bargain data plans, which are delivered sans contract, might have been a carrot in extending AT&T's hold on the iPhone for a few more months, it's not at all clear that an extension would have been necessary to lock in sales through the end of this year.