There might be less hype for this upgrade than typically is the case, because of the unauthorized leak of a prototype.
A new iPhone OS 4.0 operating system also will be debuted.
Analysts believe that the phone will be priced at a similar range as the current iPhone 3GS, which starts at $199 with a two-year contract, with the iPhone 3GS price cut to $99 with a similar contract.
The new lower price for the 3GS device, combined with AT&T Inc.'s new data prices, which lower the entry-level monthly service rate, could accelerate demand beyond the strong triple-digit growth the phone has been seeing, some believe.
"One of the impediments to smartphone adoption has been the service plan," says Shaw Wu, an analyst for Kaufman Brothers, adding that "when they make a form factor change, it's pretty powerful."
Apple is expected to sell about 36 million iPhones in its fiscal year ending Sept. 30, 2010.