When I'm in HTML View the tool bar says, "HTML View." When I'm in Text View the tool bar says, "Text View." I think that a mode change button like that should indicate the view to which you to change, not the view you're currently displaying.
For instance, if I'm in HTML View, the tool bar item should say, "Text View." This would indicate that if I want to enter the Text View, I should press the button. That way it is an "verb" and is consistent with the "Link to URL" and "Link to User" buttons that are also on the tool bar - in other words, they perform an action, they don't indicate a mode.
Does this make sense? I'm not sure I'm expressing myself very well.