That's impossible, because we have already heard that Plame's identity was not classified at that time.
I think the jury is still out on that one. We don't have a definitive answer on that yet.
We have heard that it was classified, and not classified, and covert, and not covert, and that her status didn't matter to Libby's case, except that it did matter.
I suppose it would be too easy for the CIA to make a public statement describing Plame's status at the time she was outed. Everyone on the planet now knows that she was an agent who did classified work, so I don't see how such a disclosure could harm national security.