Widely anticipated, Apple is expected to unveil the iPhone 5 on Wednesday, Sept. 12 and while techies are patiently waiting to see what the next generation iPhone has to offer, economist are waiting to see what the phone has to offer the economy. 

JP Morgan economist Michael Feroli said he believes that the release of the iPhone 5 could boost Q4 GDP by $3.2 billion, or $12.8 billion at an annual rate. 

U.S. GDP grew 1.7 percent from the first quarter to the second quarter of 2012, according to the U.S. Bureau of Economic Analysis.

Feroli said he expects that Apple will sell around 8 million iPhone 5s in the United States in the fourth quarter, and sales of previous generation iPhones will continue to sell at a solid pace.

"This estimate seems fairly large, and for that reason should be treated skeptically," Feroli warns. "However, we think the recent evidence is consistent with this projection."

Feroli expects the iPhone 5 to retail "around $600."

Last year October, the iPhone 4s became widely available and Feroli said overall retail sales that month significantly outperformed expectations. 

"Essentially, all iPhone sales occur either on-line or in retail stores," Feroli said. "Over half of the 0.8 percent increase in core retail sales last October occurred in two categories: on-line sales and computer and software sales, which combined had their largest monthly increase on record. Given the iPhone 5 launch is expected to be much larger, we think the estimate mentioned in the first paragraph is reasonable."

In the last quarter of 2011, Apple sold 37 million iPhones, twice what it sold in the same period in 2010.