Why did Apple pre-announce what they will talk about at WWDC, to lower the expectations of a new iPhone refresh. Right before any Apple event their is outstanding amounts of hype because everyone fantasizes what they hope Apple will announce, and as soon as they don't their are floods of people that rush to forums to call the event a "Let Down"
Before the iPad was announced, it had been rumored for several years, and if Apple held a music event in September were they usually released new iPods, the media and people on forums would be quick to speculate "Will this be the event where Apple finally announces their Tablet?", and if all they announced were brand new iPods, the event would have been a "Let Down" or "Lame".
I think this time Apple is trying to lower the expectations so that people can not feel let down come Monday afternoon, though clearly it hasn't been affective since some people still believe their to be a new iPhone hardware announcement.
I believe their will be some new Hardware refresh at WWDC, but it will be limited to the MacBook Air and possibly Airport Extreme Base Station and Time Capsule.
WWDC has always been about Developers and Software, so it won't be anything unusual if during Monday's opening Keynote all Apple talks about is Software.