Yesterday Apple announced the details of the WWDC 2009 Keynote. The fact that Phil Schiller is leading the keynote and Steve Jobs was not mentioned lead analysts to believe that Apple is not announcing a new iPhone at the WWDC 2009.
According to BusinessInsider Piper Jeffry Analyst Gene Munster says that there will be no new iPhone 2009 at the WWDC and Apple actually would host a special event at the end of June or early July to introduce multiple new iPhone models.
All along Apple said that Steve Jobs will be back at the end of June. If the return of Steve Jobs needs to coincide with the unveiling of new iPhones is questionable though. The WWDC 2009 has a packed program for developers, but consumers are not getting overdosed with the new iPhone 3.0 OS features and the Snow Leopard OS X news. We can take an unveiling of new hardware at the WWDC 2009, no problem.
Dan Frommer at BusinessInsider thinks along these lines and still sees also a chance that Apple uses the WWDC as the launch platform of a new iPhone 2009.

Another reason for Apple to unveil a new iPhone at the WWDC is the Palm Pre's imminent launch. If Apple is announcing a new iPhone at the end of June than the Palm Pre has one month to establish sales. Just for that I could see Apple at least hint at a new iPhone at the WWDC 2009.
More New iPhone 2009 Rumors.