I made an off-handed mention about Sony, and by connection the entire industry, ditching APS-C except for their entry-level cameras.
The more that I thought about that idea, the better it became. Canon makes two, TWO, lenses worthy of an enthusiast's attention for their APS-C cameras. At most, they make three. Those are the 60mm F2.8 macro, which is excellent, and the 17-55mm F2.8. The 10-22mm F3.5 is pretty good, so I'll play my own Devil's advocate and include it.
Three lenses. They make over sixty. It's obvious that APS-C is not something that they care about. It's obviously something that NONE of the companies care about. The only company out there who's wholly behind APS-C is Pentax, which is, regardless of the quality of the new K5, a bit player at best.
One of the major advantages to APS-C is the decreased size of the optics and the increased depth of field at any given aperture. If I am forced to use full-frame lenses, all advantages are eliminated. The only remaining advantage is increased pixel-density, which is only kinda'-sorta' an advantage.
There will be an increase in price, since sensors of larger size will obviously have smaller yields and thus higher prices. But Canon and Nikon alike both makes APS-C cameras that are just as cheap as 4/3 cameras, so with the advantages of scale, the price increase might be negligible.
Enthusiasts would jump all over this. No one has a lens set that they want to keep for APS-C, so by shifting formats, the companies aren't doing any harm to customers. Instead, the well-heeled customers are given a big boost in image quality and access to lenses that their format can actually use to their potential.
This potential should also be of great interest to the marketers and bean-counters at the various corporations. Sales of SLR cameras, after climbing by huge percentages for the past ten years, are flatlining and starting to decrease. The market is becoming saturated and the best that can be hoped for is selling upgrades to those who already have cameras. Everyone who wants a camera has one.
By introducing a new format to a wide audience, the companies net three benefits. One, they can sell new cameras as upgrades, generate new interest, and possibly lure new enthusiasts into the market. Two, they also lure more people away from cheaper APS-C lenses into their respective systems of full-format lenses, which will then lead to increased sales of their full-format cameras. And three, they finally have some real differentiation between cameras, as opposed to engineered differences where one camera is inferior to another simply because it needs to be, not for an financial reason.
Think about how great that would be. APS-C cameras cost up to $1,000. APS-H goes from there up to around $2,000. And from there on up, it's full-format. It would be a beautiful thing.
APS-C will always have a place for those who want cameras that cost well under $1,000, but for those who want more, give them something worth wanting. Sony was able to do the A850 for under $2,000. Everyone else can sure as hell manage a 1.3x sensor for a lower price.