Serebii isn't really the best place for news. Their Pokedex is pretty good but beyond that I wouldn't trust them any more than any other Pokemon fan site. They've been known to get things wrong.
They, however, don't post crap for hits, like Pokejungle does.
They are a fansite, and do get things wrong occaisionally. So does every major publication.
Including, lol, Pokejungle.
Pokejungle's also been more punctual and correct with their translated information, too. Serebii's been making updates all over the room, and that's no good.
Pokejungle lives in Japan now, Serebii in England.
I think they've beaten Serebii twice recently. Good for them. That doesn't make them a better site - in fact, Serebii, although slower, had more info from Corocoro up faster than Pokejungle, who missed a lot of stuff.