Its has been a long time, so just wondering.
In coroCoro(a thing that tells new things coming out in/about pokemon), it comes once a month, every 15th. Check out this page for all the black and white pokemon http://www.serebii.net/blackwhite/pokemon.shtml So until august 15th, we probably wont learn of any more new pokemon.
They will be announced when they're announced. Our pokemon page lists all the latest info so check back every couple days. http://pokemondb.net/black-white The page Swampert posted is good too.
As Swampert said they are revealed in CoroCoro monthly. They are also revealed on the Pokemon Sunday and Oha Suta TV shows in Japan.
It's unlikely that ALL the pokemon will be revealed before the games come out.
