WIVI will be developing their own String sections based on the same Technology, but there is an alternative right now called Synful which is also based entirely on Modeling Technology.
Synful also does Brass but I don't think their modeling technology is as good as WIVI.
http://www.synful.com/ http://www.synful.com/UserDemoSounds/Mayrand/Mayrand-Action.mp3 Personally, I'd be more interested in WIVI.
Regards
James