The launch, called "Samsung Unpacked," will be broadcast live from Radio City Music Hall in New York City on Thursday night. The new device is expected to sell as many as 10 million units in the first month it is available.

Assuming demand is that high, Samsung will need to carefully manage its supply chain, as a manufacturing issue with S III handset cases apparently cost the company lost sales of an estimated 2 million units of that model. The company said earlier this year that it had sold more than 100 million Galaxy S phones since the product line's launch in the middle of 2010. Although Samsung does not provide sales figures for individual models, analysts estimate the S III will have sold about 60 million units by the end of this month.

$401 Million vs. $333 Million

Samsung has been building up expectations with carefully leaked teasers of information, so expectations are high. By being the followup to the most successful Android smartphone and by having the worldwide launch in the U.S., Samsung is seen by many observers as directly challenging Apple's iPhone.

Android is the leading smartphone platform, and Samsung the largest smartphone manufacturer, with 30 percent market share compared with Apple's 19 percent, according to IDC. Apple and Samsung are also locked in a worldwide legal war over patents for mobile devices. Now, Samsung is experiencing the kind of anticipation for a launch event that is common for new Apple products.

Samsung has certainly stepped up to the plate in the U.S. for marketing, spending $401 million to Apple's $333 million in 2012, according to ad research firm Kantar Media, and positioning itself as the iPhone alternative. In 2011, Samsung spent $78 million.

Rumors about the S IV have been floating around for weeks. Some expect a 5-inch screen, slightly bigger than the S III's 4.8 inches, an enhanced eight-core processor, a 13-megapixel camera, and possibly a flexible screen or improved eye-tracking that scrolls the screen when the user's eyes move. In February, the company filed for a U.S. trademark for the "Samsung Eye Scroll."

'Better Focus on Usability'

Current Analysis' Avi Greengart, who will be attending the launch, said he is expecting "the usual improvements that we see to iterative smartphone designs," such as a faster processor and a better display. He is not expecting "a radical bump in screen size," because the company "addressed that need with its Note line" of smartphones that are also mini-tablets.

Greengart said he did expect "a continued focus on software functions," with a "better focus on usability" and overall software quality. He noted that the eye-tracking feature currently on the S III, which dims the screen if you're not watching it, "doesn't work very well and users need to dive deeply into the menus" to turn it on or off.

One thing Greengart is hoping Samsung improves is the physical material and design of the S III, which he said "looks and feels cheap." The S III has become so popular, he said, because "it's quite good," with fast processing, a bright display, and a marketing campaign that focuses on "the benefits, not the specs."