With that out of the way, here are my unfounded assumptions of what we’ll see on the 17th:

• iPhone OS 3.0 and Snow Leopard share the same code base – this means the best multitouch support on the desktop and the best media framework (Quicktime X) in your pocket
• New Core Location features will be added, along with a demo of a Turn-by-turn driving directions app with VoiceOver speaking street names
• Safari 4 Mobile will be shown, with an emphasis on HTML5 features as a replacement for Adobe Flash, as well as enabling offline web-apps
• Safari will most likely have a Cover-Flow like version of Top Sites
• Some announcement of how it’s Apple’s most efficient mobile OS ever – 15-30% reduction in ram use or increase in battery life
• Beta Available on the 17th to registered developers, shipping end of Summer along with Snow Leopard
• One more thing: $30/month Tethering plan from AT&T – possibly available the same day
• No copy & paste, No MMS, No background apps, NO Flash

That’s my guess, and I’m sticking to it.