You can thank the new 2010 Super GT rules for this. All GT500 class cars must now be of an FR configuration. Since the NSX is MR, Honda has officially canceled the NSX-GT program because it no longer qualifies.
Thanks Super GT.
Honda will announce a replacement for the NSX-GT soon. S2000? The canceled(?) FR NSX successor?
The last race for the NSX-GT will be on Nov 7th.
Weak.
--Conrad
Source: http://supergt.net/supergt/news/2009n/gt091023001.pdf