iPhone 5 posters have arrived at T-Mobile stores across the United States, indicating that Apple's iPhone 5 will be released on April 12, according to ValueWalk.

Also indicating the iPhone 5's upcoming release through T-Mobile, pre-orders for the iPhone 5 on the T-Mobile network are available on the carrier's web site.

Missing from the iPhone 5 announcement materials is a description of the company's UNcarrier plans, in which subscribers can purchase the phone on an installment plan. Users can then pay part of the phone's value each month for two years, in addition to their monthly fee.

T-Mobile hasn't supported any previous iPhone model, so many are anticipating an extensive advertising campaign for the mobile platform.

The iPhone 5, in addition to the updated model to be released after the iPhone 5, had already been designed before Steve Jobs' death in October 2011.

A liaison officer for Apple made the comments last week claiming that Steve Jobs had a hand in designing the most recent and upcoming iPhone. The San Francisco Examiner reported that Michael Foulkes said the designs for the next two Apple phones "preceded Tim Cook [as chief executive]."

Although it seems like two years is a long time for the completion of a phone design, industry professionals explain that such a timeline is common.

Horace Dediu of Asymco Consultancy and Nokia said, "Having worked in a phone company, I think it's a given [that the phones were designed that far back]. Work under way now is for products shipping in 2016."

He added, "Software alone does not a phone make. Hardware specifications are [determined] on a different time scale."

Apple's work on the first iPhone allegedly began in 2005, according to The Guardian.

Rumors speculate that the next model of the iPhone, referred to as the iPhone 5s or iPhone 6, will be revealed in the summer of 2013.