In my opinion, i think a camera is good as long as it doesn't stop you from evolve in photography technique and art. If you feel comfortable with and it is ok for what you are doing with it then... just continue your work with it.
When you will need more speed, less noise or faster and precise focus, then you will go one step further and upgrade the equipment.
Please don't take this as a rule, it's just my opinion!
I have a habit of getting comfortable with certain equipment, and find that something has to "retire" it (ie: snowboarding accident = camera crumpled at bottom of rocks), for me to actually upgrade. But then, I find, when I finally do have the newer tech, I can't imagine why I had waited so long to upgrade. Of course, there is always a learning curve, and I inevitably always curse some new feature, or complain about a feature that I miss. But, in the long run, I love having newer equipment.