According to the source the event will not involve any hardware at all and instead will focus on publishing and eBooks (sold through Apple’s iBooks platform) rather than iAds. Attendance will also be more publishing industry-oriented than consumer-focused.
The event will unveil improvements to the iBooks platform, according to the same source, and is not “major.” I’m still trying to track down other details, such as the exact day and time and will keep you posted. My request for more information was sent to Apple via email and has not yet been responded to.
I for one am hoping they’ll finally reveal a way to easily get Newsstand off your iPhone. I’ll update this post when/if I have more info.