I just love how a lot of people assume that this is a good thing.
Somethings to note:
-If Jon was fired, that is more than likely a sign that firaxis (or 2k) has pulled the plug on the further development of civ5. Expect no major patches or expansion from here on. Stuff like MP, will never get fixed. You just might see some extra DLCs churned out for extra $$.
-Another possibility is that Jon Shafer left because of some internal conflict, which probably had to executive decisions from the top, like releasing the game in a state, that is best described as unfinished. In any such conflict, Jon was likely the one representing your interests, because like it or not, he was "one of us". Him leaving, again probably means that he won't be replaced, or be replaced by somebody who is more willing to dance to the tunes of the executive pipers.