There are no real reason why Apple should stick to AT&T and Verizon Wireless only for the launch of the iPhone 5 in June, after the latter became the second network carrier in the US to sell the handset.
Last year, court documents apparently confirmed that AT&T had signed a five year agreement with Apple which would have given the network operator exclusivity over the iPhone until 2012.
But it seems that the contract has either been altered or dissolved before the expiry date; Apple is unlikely to have drafted a similar document with Verizon Wireless now that the iPhone brand has been firmly established as one of the leaders in the smartphone market.
The US was the last territory where a carrier had an exclusive agreement and the launch of the iPhone 5 on all four major US carriers could coincide with the arrival of a new cheaper iPhone 5 mini iteration as well.
In all other mature markets like United Kingdom, France and Germany, where the iPhone is available on several operators, fierce competition means that there are some great deals to be had.
In addition, because of its exclusive nature, the iPhone is often given preference when it comes to advertising budgets and promotions. For example Orange UK lists the iPhone and the iPhone 4 on premium spots in its online store.