To be honest, I must say that I disagree that digital photography is going to reach a point where it stops getting better. Unfortunately, it is the camera manufacturers that control this and it is not in their best interest to speed technology ahead as fast as possible. Manufacturers first resonsability is to the shareholders, to make big returns on their investments, unfortunately, we, the customers are next in line. Canon, for instance, their main priority is to make a profit. They know perfectly well that if they make a camera that litteraly can’t be beat, even by themselves, then they will continue to product that camera for a long time, without replacing it. Like it has been previously mentioned, manufacturers make their money off of several products and a diverse market, which they would lose if they made a body that couldn’t be beat.
Now this is why, we have the concept of monopoly, and that no one company can control an entire market, but lets face it, Canon is running away from pretty much anyone. Chances are that they won’t be cought for a long time. Eventually, they will probably get cocky and make some bad products in a row, allowing for Nikon and such to catch up, but this, I am guessing, is at least 5-10 years down the road.
Do I think that digital photography will reach a plateau: yes, it will, but it will be a very short one, followed by another quick steep rise. Technology is so diverse that manucacturers will always find something new and better to add to their cameras. The same thing was said about PCs. Bill Gates once said that, no person will even need more then 128 Kbytes of memory (not sure if that is the exact number). Now, with photography, if you have a PC will less then 1GB, then you are hopelessly lost. If computers are any indication, then digital cameras will continue to get better, and we, the consumers, will continue to be amazed by how better things have gotten and will will continue to dish out the cash for them.