>>26482343>>26482427They revealed the number early in Black and White's promotional materials.
In fact, they don't normally give us exact numbers (except for Gen II's pre-release, I believe) but they do normally give us a ball park of how many Pokemon to expect. To my knowledge, X/Y were the only time they didn't brag about having "over ___ new Pokemon!", and that's only because they must've known that 70 ain't no number to brag about. I'd be more worried if we DIDN'T get a rough number in the next 1-2 trailers, because that'd imply we're getting a low number