While the actual Tokyo Game Show won't be starting until Thursday morning Japan time, it's a lot like E3 in that there's normally big events taking place the day before. So, for all intents and purposes, TGS actually starts tonight.
And it starts with Sony's PlayStation press conference, which we'll be at and covering live, right here on Kotaku. There's talk Sony will be showing off new hardware at the event, perhaps a slimmer, cheaper version of the PlayStation 3. Who knows. They might even talk about The Last Guardian...*sobs*.