posted on YPKO forum...

"I looked at the picture and managed to make out D-deck. Found another link with video. I think your looking at something very new and not the Tyros 4. D-deck only available in Japan from what I can see.
http://www.yamaha.co.jp/d-deck/index.html

I don't think the Tyros 4 will be that drastic and will remain a single keyboard. I personally don't need a second keyboard and the extra weight (bulk). Give me top technology in a compact portable keyboard. For now the T3 is awesome for me, my needs, and of course sound results."