I think this only applies if the two actions occupy the same space, and change when pressed? If I saw a separate play and pause button, I'd assume play means play and pause meant pause. If I saw only one button for play, I'd probably assume it was currently paused/stopped.
My bad, I should have been more specific in my post. I was talking in the context of software which in most music players has the pause and play buttons occupying the same space. On physical devices such as dvd player I obviously consider the pause button as "to pause" and the play button as "to play"