Ring every bell in every tower: The beast is slain! For the first time since Apple's iPhone 4S debuted in October 2011, the phone has been dethroned as the number one selling smartphone in the United States. All hail the conquering hero: Samsung Galaxy S III.

Selling more than 10 million Galaxy S III smartphones, and more than 10 million Galaxy Note phones. Samsung has flexed considerable muscle this summer. During the second quarter, the company shipped nearly twice as many smartphones as Apple. What remains to be seen is whether the company can hold on to its market position once Apple begins selling the iPhone 5, widely rumored to be released Sept. 21.

In August, the Galaxy S III replaced the iPhone 4S as the top-selling smartphone in the United States, Canaccord Genuity analysts wrote in a Sept. 3 report.

In May and June, the iPhone 4S was the top-selling device at AT&T, Verizon Wireless and Sprint. On June 21 the Galaxy S III became available in the United States, and by July, it was sharing the title with Apple, leading sales at T-Mobile (which doesn't offer an iPhone) and Verizon while the iPhone continued to dominate at AT&T and Sprint.

In August, the iPhone 4S held on only at AT&T, with the Galaxy S III as the carrier's second-best-selling phone, while the Galaxy S III dominated at Verizon, T-Mobile and Sprint. At Verizon, the iPhone 4S was even outsold by the Motorola Razr Maxx, also priced at $199.

While sales of Apple's 10-month-old phone are understandably slowing at this point, Canaccord analysts fully expect a strong Apple comeback.

"Our checks indicated strong consumer interest in and likely demand for the iPhone 5, and we believe Apple will return to strong No. 1 smartphone share in the U.S. post the iPhone 5 launch," according to the report.

On Sept. 4, Apple sent out enigmatic invitations to an event on Sept. 12 at which it's expected to introduce the iPhone 5. If the rumors are correct, Apple will begin selling the device Sept. 21. And if analyst forecasts are correct, Apple will sell a record number of smartphones.

"We anticipate an LTE iPhone 5 with a new hardware form factor will result in record iPhone sales and result in Apple reclaiming top share in the U.S. market," wrote the Canaccord analysts.

"We believe Apple's growing international channels and growing iOS base position Apple for extremely strong December quarter iPhone sales and very strong market-share gains during the important holiday selling season," analysts wrote. "As such, we believe Apple will post very strong December quarter results, regain global smartphone share during the holiday selling season and grow its leading share of industry profits."

Analysts at investment firm Jefferies are also primed for record-setting sales. In a recent research note, they wrote that the newest iPhone "will be the biggest handset launch in history."

But until then, the market is Samsung's. The company sold 50.5 million smartphones during the June quarter, according to the Canaccord report, and will continue to dominate through September. Once the iPhone 5 launches, the report noted, "we anticipate Samsung will continue to dominate Android smartphone sales but lose share to Apple during [the fourth quarter of 2012]."

Piper Jaffray analyst Gene Munster, in a Sept. 4 research note released after the Apple invites reached inboxes, wrote that should Apple indeed begin selling the iPhone Sept. 21, one week of sales could add 5 million more units to Apple's September total, driving it to approximately 28 million units.

Apple sold 1.7 million iPhone 4 devices during its first three days of availability; and sold four million iPhone 4S devices a year later in the first weekend alone.

According to AllThingsD, Wall Street is expecting 22-23 million iPhones to be sold during the September quarter alone, but crucially it's a good way-away from the Christmas holiday sales where many previously-bought contracts end and sales typically rocket through the roof.

J.P. Morgan analyst Mark Moskowitz said also today in a research note that the new iPhone 5 will "not be hampered by chip and display-related supply chain shortages" as previously expected.

He expects sales volume to balloon by late September for the new iPhone, and a similar patch of high volume selling for the dubbed-'iPad mini' in early October.

"We are not concerned about a 'mini' (iPad) encroaching on Apple's current tablet penetration opportunities. We think the iPad mini will target the budget-conscious consumer or the e-reader focused end user, implying the device offers incremental penetration opportunities. Meanwhile, we do not expect enterprise- and education-based end users to gravitate to the smaller screen size of an iPad mini.

Moskowitz avoided giving defined figures, but gave a revised estimated that Apple will sell around 168 million iPhones and 91 million iPads in total by the end of fiscal year 2013.

By comparison, Apple sold more than 85.9 million iPhones in total in the U.S. since its launch in Q2 2007 up to Q2 2012, according to earlier court filings that were outed during the Apple v. Samsung patent ding-dong.

"We expect both product lines to offset weakness in Mac and iPod," he said.