the "demos" that were posted for the WK 7500/CTK 7000 use the WK 500 engine, because the composer did not have a ready prototype in time.
At least that's what they claim here:
http://www.youtube.com/watch?v=xq9i-l6JsGw&feature=related be sure to watch the videos in 720p to get the best audio video quality.
In the comments there is also a Russian who supposedly saw the keyboards in Moscow, didn't like the "new" sound source and is bitching about it.
[This message has been edited by trident (edited 11-15-2010).]