Six million smartphones over the span of one weekend is an impressive figure, and if Apple, Inc. (NASDAQ:AAPL) achieves this with the release of the iPhone 5, the sixth-generation device would become the hottest-selling iPhone on its first weekend of sales.

According to analyst Horace Dediu of Asymco, the sales of the iPhone 5 from September 21 to 23 could reach up to 6 million.

The iPhone 4S, which was released last year, sold 4 million on its first weekend, which was already more than double the 1.7 million units sold by the iPhone 4 on its first three days in the market. Going even further back, the iPhone 3GS sold only a million first-weekend units.

The Asymco number-cruncher added that most of the iPhone 5’s buyers may be repeat customers who have developed some sort of brand loyalty with Apple and the iPhone. He didn’t discount the possibility of several first-time iPhone buyers, however.

Dediu also cited the fact that Apple will be launching the iPhone 5 in 31 countries over its first two weeks – nine countries, including the U.S. on September 21, followed by 21 European countries and New Zealand on September 28. This large-scale launch may also contribute to the record numbers forecasted.

On the technical side, the new iPhone is the first Apple smartphone to support the high-end 4G LTE, or Long-Term Evolution connectivity standard, and also the first to include a 4-inch screen. It would be debuting Apple’s new and improved iOS 6 mobile operating platform, which will also be compatible with a few other Apple consumer electronics products, such as the iPad 2 and 3 and the iPhone 4 and 4S.