I would suggest that for the vast majority of amateur photographers, (excluding those with specific need for, say low light, or fast multi-frame ability), any of the currently available DSLR's from reputable manufacturers will provide final image quality of all and more than they will ever need.
There seems to be never ending discussions about the need to "upgrade this camera for that", or, "I should have gone for X instead of Y" etc. etc.
The bottom line with this school of thought comes down to one of two things: -
Either - People want to upgrade simply for the sake of having a newer, all singing and dancing, and (percieved) better camera, so that they can be "one-up" on their friends and aquaintances. OK if they want to waste their money - but ultimately, they will be judged on their results and not on what equipment they own.
Or - People are simply not getting the best from their current camera, and are under the impression that an upgrade will solve all their problems. In which case no amount of upgrading will improve their results.
My suggestion (for the DSLR user) is: - buy a decent camera to start with -
and stick with it until it no longer works and becomes economically irrepairable.
Spend your money wisely on lenses. A bad lens will ruin the image quality of even the most expensive camera.
Constant upgrading of camera bodies will do nothing for your photography (but your dealer will love you.
).
Regards
Mike.