[ThinkQuick]

Over a longer period of time, of course yo are correct, as anyone knows you must cap a bottle of pop to prevent it from losing its carbonation.

However, over a small period of minutes, there will be a minimal amount of equilibration / loss of carbon dioxide.

Picking up the bottle and moving it about as you replace the cap could easily introduce more fresh air and mix it with the pop, causing a much more rapid loss of carbon dioxide. This is probably not offset by the extra few minutes the bottle spends closed. Even if the difference is significant I think the effect will be minimal and certainly not worth yelling about.

Note however, if the cap is indeed lying beside the bottle and you replace it in a nonviolent way, then as bobman says, this will certainly keep the pop carbonated longer