Business Insider is quoting Piper analyst Gene Munster as saying:

No New iPhones [at Apple's World Wide Developers Conference]. As indicated in today's press release, we believe Apple will focus on the new version of Mac OS X, Snow Leopard at WWDC. While some investors may be expecting Apple to launch redesigned iPhones at WWDC, we do not anticipate the launch in early June. Rather, we expect Apple to host a special event in late June or early July to launch a family of iPhones. We continue to expect multiple models, possibly a high-end iPhone with improved specs from the current version and a low-end version with lower capacity and fewer features along with a reduced pricing plan. Such a model could also be used in Apple's launch of the iPhone into China as soon as the end of summer '09.

Analysts are about as accurate as weathermen when it comes to predictions one month out, so take this with the usual Mac Pro sized grain of salt. Apple has used the last two WWDC events to showcase the iPhone, and introduced the iPhone 3G and MobileMe at WWDC 2008. If they stick to pattern, we should see an update on iPhone 3.0, the next generation iPhone, and perhaps a MobileMe refresh at WWDC 2009.

However, WWDC being an developer-focused event, it's not impossible Apple will focus on their Mac OS 10.6 Snow Leopard and iPhone OS 3.0 exclusively, leaving the hardware for a sexier consumer event later in the month.

As to a family of iPhones, we still don't see Apple breaking the software platform, which means a low end iPhone could only be a low-storage iPhone 3G (8GB?) at $99?, with the next generation unit (at 16GB and 32GB, along with other new features) taking the established $199 and $299 positions.