Interesting ... The question of updating the body is very personal, if you are satisfied with the results your camera hands you, here comes the question, why change?
If you are photographing as a hobby, the question of money is the main factor to initiate the changes.
if professional photographer, the question of upgrade will be investment in vocational careira.
I see one way; Shoot for myself and for hobby, body change only if it is even necessary.
ps: sometimes the hobby is expensive, and if you follow the whole release.
sorry for my English