Yeah...no. How could Serebii get in trouble for mentioning the two Pokemon on Pokebeach? They're not going to take down fan sites that promote sales of the game. If they were going to take down serebii for that, they'd much sooner take down the site for posting corocoro leaks. They don't for the same reason Manga companies initially weren't beating down the doors of sites like Onemanga....the fact that onemanga is now making a profit off of advertisements is the source of controversy now for manga aggregate sites. Serebii mentioning information could not endanger his site. Even if it were somehow worthwhile to get upset about and pursue legal actions against those who leak the information, serebii has just as much protection posting those images as he does posting any of the other "illegal" leaked content about the games. Nintendo / gamefreak simply would not care about that though.
Gutalala Sudalala ONE PIECE, IT EXISTS! - The Great Pirate, Edward Newgate "Whitebeard"