I don't think it's nintendo's place to announce Pokken. It's more of Pokemon Company and GameFreak's decisions.
GameFreak probably has nothing to do with it, if it really is a Namco/TPCi collaboration.
I also don't think they'd cannibalize any SSB sales with just an announcement, especially if the release date was just 2015. If anything they could use Lucario as some kind of promotion for it.