The biggest excitement, clearly, is the market of second camera bodies for people who already have one good body. It looks like we're starting out with live-view compacts, and that's fun, but I'm pretty sure that there are some other ideas out there. I've got a few brainstorms:
So, if you have a 35mm full-frame lens on an APS-C sensor camera... and most folks have at least one... you have the sensor sitting smack dab in the middle of an image circle. This means that much of the light in there is wasted.
But it doesn't have to be that way. Ever see a view camera with bellows? All you need to do is move the sensor left and right or up and down and you can get some of the advantages of a tilt-shift lens... the shift part. There's probably some limits to how complex you can make it before it won't be able to hold the sensor still, but other than that, you could also tilt the sensor.
This is a Bob Atkins idea, but there's no reason why it shouldn't work. Basically, when you use a 35mm full-frame lens, you are wasting a good sized chunk of the image circle that the lens is able to project an image inside of. So why not make the sensor wider? It'll have a few more megapixels in "panoramic" mode, still be able to fit APS-C lenses that might extend into the body of the camera, and less expensive than a full-frame camera.
By the same token, you can make a square sensor or a 4:5 sensor for a camera and fit it inside the image circle instead of the bounds of an APS-C sensor.
Sometimes you want to go from a color picture to B&W so you can really mix and mask your channels. But sometimes it's OK to use a single colored filter. If you just isolate the red channel on a digital picture, you get a quarter of the resolution because you are using one out of four pixels. If you isolate the green channel, you only loose half the resolution.
To do this, all you need to do is replace the Bayer mask (which is usually glued to the sensor) with an equivalent amount of glued plastic and adjust the software. It's entirely possible to make it a special-production item. Or you could build in a color-wheel so you didn't need to carry filters that could also help keep the sensor clean.
I think there might be a huge opportunity for somebody to sell partially-complete camera bodies to a third party for various specialized designs. Kind of like how people now buy bodies on the open market and convert them to IR bodies. If you got the body only partially assembled, I bet it would be faster and therefore less expensive.
You can make a "scanning" digital back. This works pretty much like a desktop scanner -- it moves a scanning element across the frame. So it wouldn't be that hard to re-design a full-frame body that worked as a scanning sensor, although it may be more useful as a toy camera than a high-end device. Something to think about, especially if somebody was able to cook up one at a reasonable price.
It's pretty clear that there are some live-view bodies on the way into the marketplace, but nobody knows what they are going to look like. I'm betting at least some of them are going to have the same high-end vague impression of a rangefinder look that the G9 and LX3 series have but will just have an LCD and maybe an optical viewfinder. On the other hand, I know that Leica is probably dying to do this...
My Polaroid Automatic 100 has a rangefinder and bellows. So you can see the connection lever that moves the rangefinder portion of things side to side.
What happens if you replace that mechanical lever with a motor and lenses that communicate the distance? A digital rangefinder!
Canon's got teasers out for their 5D replacement that everybody knows is going to be out real soon. Will it just be a 5D Mk II? Will it be three cameras? Will it finally have the "make my picture not suck" button? Probably not!
Mostly I'm just chuffed that I called samsung's answer to the four thirds system before it hit the news, so I wanted to be able to throw out some left-field thoughts and see if I could do it a second time. :D