Nintendo will be presenting an hour-long conference at the Games Convention in Leipzig, Germany on August 23. Their conference will take place at 10:15 Central European Time and is titled "Wii Prove Our Promise".
We don't, as of yet, know what Nintendo will be presenting at this conference, but it's very close to the September announcement Nintendo has said it will make announcing release plans for its upcoming Wii home console. It's impossible to say for certain what Nintendo will say or do on that date, however.