The iPhone 4S was unveiled on Tuesday and immediately underwhelmed fans who had envisioned a revolutionary design after a wait of more compared to 15 months.
But Wall Street analysts are betting which hardware updates and software enhancements, including a well-reviewed voice-recognition software program system, will pull in buyers.
AT&T, Verizon Wireless and Sprint began taking US online orders for that device on Friday.
Comparisons are difficult because the iPhone has become carried by three wireless operators, versus just one. This past year AT&T was the only carrier to sell the telephone. But the previous generation of the smartphone, the apple iphone 4, was the fastest-selling mobile in Apple's history, with 1. 7 million devices selling within the first three days.
Estimates vary, but some analysts expect Apple to market about 27 million to 28 million iPhones in the actual October-December quarter.
The latest iPhone 4S hits store shelves all over the world on Oct. 14. It debuts at a critical point for Apple.
Phones based on Google Inc's Android -- for example Samsung's Galaxy -- are providing heightened competition just like a new CEO, Tim Cook, takes the reins.
Jobs, who died on Wednesday following a long battle with pancreatic cancer, ceded the top work to Cook in August. Some analysts say people trying to commemorate the legacy of Apple's iconic co-founder may scoop in the very last iPhone to be unveiled in his life time, giving sales a bump.
Apple was not immediately readily available for comment. Sprint iPhone sales were not mentioned during a good unrelated news conference by Spring on Friday.
Shares within Apple were holding steady at $370 in after-hours industry.