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Currently there are 19 Pokemon officially revealed + 21 that we know exist thanks to trailers/leaks but haven't been officially revealed. When you factor in all the unannounced Pokemon journalists saw in the first 90 minutes, pokemon that seem obviously unevolved like Wooloo, Rolycoly, and Impidimp, plus the fact that they're intentionally hiding a bunch of info, there will probably be at least as many new pokemon as XY.