Those concerns are reflected in Apple's stock price, which has declined nearly 30 percent since peaking at $705.07 at about the same time the iPhone 5 went on sale last year. The Standard & Poor's 500 index has risen about 14 percent during the same stretch.
Even though Apple's market value of roughly $460 billion is more than any other company in the world, the deterioration in its stock price is escalating the pressure on CEO Tim Cook to prove he's the right leader to carry on the legacy of co-founder Steve Jobs. Since Cook became CEO two years ago, Apple has only pushed out new versions of products developed under Jobs.
In public appearances, Cook has repeatedly said Apple is working on some exciting breakthroughs, but he hasn't revealed details. The company is believed to be working on a so-called "smartwatch" that would work like a wrist-bound smartphone. Samsung Electronics, one of Apple's biggest rivals, introduced its own $300 smartwatch called Gear last week, as did Sony and Qualcomm Inc.
It's unclear whether a smartwatch will be on Apple's Tuesday agenda.
The company isn't expected to reveal the latest model of its tablet computer, the iPad, until later in the fall. Apple introduced a smaller, less expensive version of the iPad last year in response to the success of more compact and cheaper tablets running on the Android system.
This year's refresh of the iPhone line may address the growing popularity of cheaper Android phones. Based on leaks from suppliers, it appears Apple is poised to release a less elaborate and less expensive version of the iPhone in an attempt to appeal to consumers too frugal or too poor to pay for the high-end model that sells for more than $600 without a wireless contract.
Apple declined to comment.
A new version of the high-end iPhone also is expected to be revealed Tuesday. The top-of-the-line model, expected to be called the "5S," will be the first to be sold with Apple's revamped mobile software, iOS 7, already installed. The new system, which will automatically update apps installed on the device, can be downloaded on the iPhone 4 and later models, as well as on the tablets beginning with the iPad 2.
There is also speculation that the high-end iPhone will be sold in a golden color to supplement the product line's more prosaic choice of black or white.
If there is a gold iPhone, it would be the latest sign of Apple's intensifying focus on China, the world's most populous country. The color gold is considered to be a sign of good fortune in China.
A less expensive iPhone would also help Apple boost sales in China and other less-developed countries where people don't have as much disposable income as in the U.S. and Europe.
In an unusual move, Apple has invited media to another event in Beijing that will be held a few hours after the gathering at its headquarters. The Beijing event has fed speculation that Apple has lined up a deal to sell its new iPhones through China Mobile, the country's largest wireless carrier. It is an alliance that Cook has been openly courting. The Wall Street Journal last week cited anonymous people who said Apple is preparing to ship iPhones to China Mobile.