Save yourself the disappointment man; don't hype yourself up on unofficial sources. Until PD mentions in some way that the good old NSX will pop up 'soon', no-one can confirm whether that NSX has been prepped for GT Sport.
Data-wise, the Acura could've been used as a placeholder during testing and this 'glitch', if it is one, could've brought that testing information back up. It seems logical as Acura is pretty high up alphabetically in the GT6 brand list, therefore it's the first bit of info they grabbed.
And as pointed up before, most likely the picture that showed loads of NSXs was Photoshopped, again using the logical thinking to make it seem believable.
For now, you can just dream, revert to older GTs or make an attempt to replicate an old NSX with the livery editor... somehow...