not necessarily...some shows may be presented in LetterBox which would give you the bars on top and bottom. Granted, there aren't that many shows presented in LB format.
The only one that comes to mind was HDNet's presentation of Star Trek: Enterprise. I know for a fact they shot that show in HD, but for whatever reason, HDNet decided to show the LB version. So I had bars on the side AND on top and bottom. I don't like stretching SD content.