The only time Nintendo has had an appearance in Tokyo Game Show, was back in 1996. This year, however, is rumored to be different. According to Kotaku, Nintendo plans to have a huge booth:
"Multiple, highly placed insiders confirm that the company will be in appearance, which is one of the reasons why TGS this year is four days this year instead of three."
How come? Square-Enix's Dragon Quest IX, of course. Looks like Nintendo admits Dragon Quest IX to be their next Nintendo DS top-seller.