The FAQ and Known Info thread at the top would have answered this for you.
But to clear a few things - they announced that they would be out Spring 2010 (May-March) in America and Europe, although you can basically count on the fact that America should get it first. (Europe have more things to change, more languages to translate into, more game changes thanks to European laws such as the aformentioned Game Corner slot game 'censoring'...) Places like Australia can, based on other game releases like Platinum and less to do than Europe (after all, what translating process? It stays the same as the American English... =/) expect HG/SS to come out in-between America and Europe.
Beyond that, we don't know anything about the release dates. Only take info confirmed by Nintendo, or published to be true on sites like serebii.net.
And now I'm going to close this. No point discussing a fact known for at least a couple of months atm...