Is the iPhone 4S the iPhone 5? No. Will it still sell like hot cakes? Oh, yes.

Demand for the iPhone is huge. In a Sprint strategy session Friday morning, Sprint Nextel chief executive Dan Hesse said that the iPhone is the “number one reason” that customers have left its network in the past.

Analysts looking at what’s coming up for Apple’s next handset agree that the phone will be a huge hit.

In his note to investors after the phone was released, Sterne Agee’s Shaw Wu said that the 4S is still the best smartphone on the market, with the “key differentiator” of Siri’s voice integration, which appears to work much better than voice integration services on other phones.

Adding carriers Sprint in the U.S. and KDDI in Japan, he said, will also give the phone a sizable boost.

Apple’s iPhones have amazing staying power as well. In a Tuesday interview, Gartner analyst Michael Gartenberg pointed out that the iPhone 4 was still selling well after a year on the market.

“There aren’t many phones that are over a year old that consumers can even still name,” he said.

He added that Apple didn’t have any problems selling its previous “S” phone — the 3GS — despite also being an evolutionary rather than revolutionary new design. He also highlighted the importance of adding Sprint to the mix of carriers and opening up the iPhone market for people who couldn’t afford the phones before.

And do analysts think that the news of Apple co-founder Steve Jobs’s death will have any effect on the phone’s sales?

Reuters reported that Janney Montgomery Scott analyst Bill Choi thinks store traffic and “sentiment-related purchases” are likely to get a bump, but nothing on par with the spike music sales see when a popular artist dies.

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