iPhone 3GS, Marble Delayed, Tablet Exists?

John Gruber articulates what he believes we'll see at tomorrow's keynote. Gruber first reiterates his predictions from before regarding the iPhone update:

I expect Apple to announce updated iPhones with significantly faster processors, twice the RAM, and twice the storage. I expected prices to remain the same as the current lineup: $199/299 for 16/32 GB, respectively. The video camera is going to be a major selling point.

And also reveals that "iPhone 3GS" is the codename for this next gen iPhone. It may or may not carry over to the official brand name and he is not sure what the "S" stands for.
Meanwhile, he offers some speculation about how much Apple might charge for Snow Leopard but does not believe the rumored "Marble" interface will actually make it into this version of Mac OS X:

But while I am convinced that "Marble" is a real design project at Apple, I no longer believe it is slated for Snow Leopard. A new visual appearance isn't something Apple can spring on third-party developers at the last moment. If they plan to ship Snow Leopard soon say, by the end of August that just isn't enough time to allow developers to update their software to look good under a new UI theme.

Finally, he is convinced the Apple Tablet is real but that we won't see it tomorrow.

Gruber has been known to have some inside knowledge of Apple's plans and his last-minute predictions can be quite accurate. MacRumors will have live coverage of the event at MacRumorsLive.com and we will have our own rumor roundup posted shortly.