Nikon just announced their latest camera.. the D7000... some early reviews are saying things like "the most capible camera of its class ever.. beating out the Canon 60D by miles.." etc etc.. So what to do? Do we all just run out and buy it because it is the most amazing camera "of its class" ever?
Seriously.. the only people who win in the Great Camera Arms Race are the manufacturers and retailers.
Case in point.. I got the Canon 40D in 2007.. had to have it.. got it right when it came out.. of course for me it was a huge upgrade. I had been using the XT for three years and it was just time. Here we are three years later and I still use it. (as a side note I still use the XT occasionally as well) While I moved up to full frame with the 5DmkII the 40D still has a place for me in my tool box.. I do all my studio shoots with it.. and when I need that extra telephoto range I put my 70-200 on it and shoot away. My wife uses it as her primary. Do I have any real motivation to upgrade it to the 60D? Or even the 7D? No.. it suits me fine as is. There just arn't enough feature/performance upgrades to warrent spending the money... and I could care less about having an "outdated" camera.
(well.. since the 5DmkII is my primary at the moment I really don't have that "outdated" issue anyway.. but it really is in a completely different class)
I have always felt that photography is more about the photographer then the equipment. (yes I know this isn't a new thought) Give a good photographer any camera, regardless of capability, and he should turn out something with it.. give a bad photographer a good camera and they may not even know how to get 25% of the capability out of it.
Yes.. higher performance and more features may allow you to do things you were not able to do before.. example: getting cleaner images at higher ISOs allowing you to get better shots at lower light... or faster continuous shooting for moving targets.. but in most cases only a knowledgeable photographer will be able to take advantage of them to the fullest. A better camera does not improve your composition ability.. nor does it improve your eye... or give you better judgment to tweak your exposure ever so slightly based on your subject...
We just have to accept the fact that every year or so Canon/Nikon/etc are going to come out with a new version of their cameras.. Unless you are rich you can't (shouldn't) really keep up with that. There is no point. there will always be something out that has higher megapixel.. or faster shooting rate.. or some new fancy video capability.. but none of that is a guarantee that you will improve as a photographer just by using your credit card.