Wal-Mart appears to be going it alone in slashing prices on the iPhone 3GS—at least for now.

The mass-market retailer on Tuesday lopped more than 50% off the price of the 16GB version of the most current edition of Apple's smartphone, bringing it from $199 to $97.

Other outlets, however, had failed to match Wal-Mart's cut as of midday. The Apple Store, AT&T (the exclusive network provider for the iPhone in the U.S.), and Best Buy were all continuing to offer the 16GB iPhone at the $199 list price.

It's expected, however, that Wal-Mart's rivals will match the price cut in the coming days. Meanwhile, all iPhone sales outlets, including Wal-Mart, maintained the $299 price tag for the 32GB version of iPhone 3GS.

The price cut is fueling speculation that Apple will launch the iPhone 4G at its WorldWide Developers Conference, which starts June 7 in San Francisco. Electronics manufacturers frequently cut prices on old inventory before introducing a new product.

The iPhone 4G rumors kicked into higher gear Monday when Apple confirmed that CEO Steve Jobs will deliver the keynote address at the conference. Jobs missed last year's event after reportedly undergoing a liver transplant.

Whether at WWDC or at a later event, the betting is that Apple will indeed launch a faster, 4G version of the iPhone, running iPhone OS 4.0, at some point in 2010.

Just weeks after an Apple engineer left one on a barstool in California, another iPhone 4G prototype was spotted earlier this month. Bloggers at the Vietnamese tech site Taoviet posted pictures of a device, labeled APL0398, that was similar to the phone lost in March by engineer Gray Powell.

Apple isn't providing specifics about Jobs' WWDC keynote. The company said only that the conference will feature five technology tracks, including Applications Frameworks, Internet & Web Graphics & Media, Developer Tools, and Core OS sessions.

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