Apple Inc. (AAPL)'s debut of its redesigned iPhone will test anew its high-stakes strategy of once-a-year upgrades for a product that accounts for about 70 percent of the company's profits.

The new phone, to be introduced tomorrow by Chief Executive Officer Tim Cook, will probably have a new hardware design, including a bigger screen and thinner body, as well as new mapping software and compatibility with speedier next-generation data networks. Analysts predict the iPhone may be among the biggest consumer-electronics releases in history. Still, Apple's reliance on the device leaves Cook little margin for error.

"The iPhone is the make-or-break product for Apple," said Sarah Rotman Epps, a mobile-phone industry analyst atForrester Research. (FORR) "Apple has the undeniable lead, but to stay on top they need to keep innovating."

Almost one year removed from the death of Apple co-founderSteve Jobs, the newest iPhone faces a growing army of competitors looking to grab a piece of a smartphone market that Bloomberg Industries estimates was worth $219.1 billion last year. Samsung, Google Inc.'s Motorola Mobility, Nokia Oyj (NOK1V) and HTC Corp. (2498) are among those taking aim at Apple by introducing dozens of new devices each year, instead of just one.

The new iPhone will be Apple's first change to the handset's hardware design since 2010, raising anticipation among customers who have been holding off on buying a new smartphone.

The company garnered 43 percent of its $108.2 billion in sales last year from the iPhone. And because wireless carriers such as AT&T Inc. (T) and Verizon Wireless subsidize the roughly $620 Apple gets for each iPhone sale, the device accounts for about 70 percent of its profits, according to Sanford C. Bernstein & Co. IPhone sales last quarter alone reached $16.2 billion, 33 percent higher than Google Inc. (GOOG)'s total sales and almost as much asMicrosoft Corp. (MSFT)'s $18.1 billion.

Apple's new iPhone could contribute as much as a half a percentage point to U.S. economic growth in the fourth quarter, according to analysts at JPMorgan Chase & Co.

Eoin Treacy's view Analysts have run out of superlatives in describing Apple's remarkable success. No fluke, this has been due to a steady stream of groundbreaking products, so stylish that they are the must-have consumer items for many people.

Successful products generate competitors, which is good for consumers. It will be very interesting to see how long Apple can stay ahead of them. Meanwhile, the share (weekly & daily) is overextended relative to its 200-day MA once again, which means that it is susceptible to some mean reversion towards that trend smoothing average. We are about to find out if Wednesday's launch can delay a temporary pullback. (See also Eoin's comments below.)