Man, this sounds very very interesting. I've seen reports about flat panel iMacs and G5s on the rumor sites, so apparently Apple wants us to believe something else - or something more is coming.
I won't rule out the flat panel iMac, but there's got to be something special about it. For one thing I think Apple may be ready to drop the G3 across the whole product line. It's 2002 now - the time has come.
As far as I know gigabit Ethernet is still expensive, so I don't think it's possible for Apple to drop 10/100 completely yet.
Apple has been working for some time trying to get the graphics cards to somehow natively support the layering and effects in Aqua. I believe they've had enough time to work this out and it's possible we might see some amazing new capabilities added to Aqua that take advantage of new graphics cards. I'd go even further than that, in fact, and speculate that such a card would also incorporate font rendering and display PostScript as well, with full support for Quartz rendering on the surfaces of 3D objects.
There will be a revolutionary new 3D architecture able to render objects built from bezier curves in 3D space and generate various surface maps and deformations from procedural / fractal waveforms. The composite result of all these new technologies will be objects that lose no detail no matter how much you magnify them.
As long as we're Thinking Different, I'm going to imagine the ultimate combination of all these factors, with DDR RAM, an amazing new BUS architecture, and perhaps a new slot architecture to replace the venerable 4x AGP thrown in for good measure. All these amazing new features will live in an expandable box larger than the Cube that connects to a digital flat-panel specially made for the new machine.
In the spirit of ultimate integration the new display architecture will include a built-in television / radio tuner and DVD decoder, on-board DivX support, and the further capability of rendering any of these video sources directly on the surfaces of 3D objects.
Apple won't stop there, of course. Taking advantage of new developments in holographic storage technology the new Macs will have no hard drives. Instead all data will be optically stored into a crystal lattice in a cube made of artificial diamand doped with gallium arsenide. Each 1cm x 1cm x 1cm cube will hold 32 terabytes of information. Data transfer to and from this new storage meduim will be instantaneous.
Not content to stop with AltiVec, Apple will make use of their secret research in neural networks to bring us the first computer that can process analogies in natural language. The new Inference Engine won't process the kind of data that need bit-level accuracy but will instead be capable of taking creative routes and making strong intuitive guesses. Because it's a Neural Network it will learn from you as you work, adapting to your style of working. Before long your Mac will be able to guess what you want - before you want it.
As if that wasn't enough, Apple engineers will come on-stage to personally unveil the most advanced Quantum Computer ever built. IBM's recently-announced seven-atom Quantum Computer can only solve one simple problem. The Apple Quantum Engine will be able to compute all possible combinations of any problem in zero-time, making all existing encryption methods obsolete.
A special hub will connect the Quantum Computer, Neural Network, and Holographic Storage together in a unique way that allows them to share data freely. Photoshop operations that take two minutes on a 2GHz Pentium IV will occur instantaneously on the new Power Macintosh QNH. Final Cut Pro will render transitions and effects - you guessed it - instantaneously. Virtual PC 5 on the new machines will run Windows 6 times faster than the fastest Athlon.
At the end of the Keynote Steve will appear to walk off stage - but suddenly come running back. "Oh wait," he'll say with a sparkle in his eye, "There's one more thing I almost forgot." At this point Bill Gates will be wheeled out on a gurney strapped down with piano wire. To the amazement of everyone Bill will smile and announce that he has decided to make his greatest contribution to the Mac community, the sacrifice of his putrescent miserable life. At which point the entire audience will erupt into a riot, demanding that Bill simply have his limbs amputated and chanting "Poor misguided Bill! It's Ballmer we want to kill!"