While I am not sure how long this has been up, I have found a Japanese site dedicated to two bemani games, Guitar Freaks v3 and Drum Mania v3. The site is ran by Konami and while it does not have any direct screenshots or video of either game, by using the translator you can get a basic idea of what is being talked about. They have just completed the third round of testing for Guitar Freaks v3 in Japan and the site mentions Battle Mode a couple of times, which is obviously the 2 player mode. On top of that it mentions a 2nd Battle Mode where you can “rival the entire country”, which sounds an awful lot like an online Battle Mode. No word on any US version, but since the game was seen at ATEI 2007, we can keep our hopes up.
[Link to the translated version of the Guitar Freaks v3 page]