Face it, Nintendo is notorious for being a control freak.
With E3 no longer what it once was and Spaceworld unlikely to return, I think the days of Nintendo unveiling games and making announcements at shows are coming to an end. Basically, like P666 says, it will probably be all press-releases and SSBB-style online reveals from here on. Personally I'm fine with that. Instead of waiting all year for one big show that people over-hype to oblivion and pretty much guarantee disappointments, we'll get completely unexpected reveals on random days whenever Nintendo damn well feels like it.