Two different animals. The first generation is an icon and a classic and this status will only increase and getting stronger with time.
The new one will have to gain this status and it will in any way alter the first generation status.
I would never trade a first generation NSX for the second one. Only try to get both. OTOH, I just can't see how a 20-30k$ rebate ( first gen NSX mean value ) would be so attractive or would be so significant in determining if you can afford or not the new one ...
If you can qualify for 100k$ on a 130k$ car, it shouldn't take too much time to get the remaining 30k$ ? Not worth letting go your actual NSX, just wait some more time to get the remaining amount of money or buy a second hand new NSX ...