Amid the frantic rumors in advance of Apple’s Tuesday announcement of its new iPhone, there’s this from Joann Lublin and Spencer Ante of the Wall Street Journal: that Sprint, the No. 3, cellular provider in America, is all but betting the company to offer the iPhone to customers.

According to the Journal, Sprint’s CEO, Dan Hesse, told his board the company “would have to agree to purchase at least 30.5 million iPhones over the next four years — a commitment of $20 billion at current rates — whether or not it could find people to buy them, according to people familiar with the matter.”

That would mean Sprint would, at best, not break even on the deal until 2014, said the Journal. But the company may have no choice. It has been sinking for five years. Not being able to offer the iPhone is “the No. 1 reason customers leave or switch,” Hesse said at an industry conference in September.

Sprint Nextel trudges along behind market leaders Verizon Wireless and AT&T — and AT&T is trying to merge with T-Mobile, the No. 4 company. The iPhone could make a big difference. Bill Choi, an analyst for Janney Capital Markets, is quoted today as saying Apple could ship 107 million iPhones next year.