For some reason, my replies are still not showing up on this thread and others, but let's try this again:
I don't think people looking to purchase a new NSX are going to cross-shop with a C8, just like people looking to buy a Porsche Cayman don't cross-shop and look at a new NSX. The price points are too far apart. People shopping for a new C8 will most likely stay within that price range plus or minus $10K, maybe $20K. Now there may definitely be people cross-shoping a new C8 with a used NSX, and that could affect used NSX prices if the NSX owners get desperate and want to sell quickly. However, I think that desperation would be the exception and not the norm.
From all of the new NSX owners that I've talked to, which admittedly is only a handful, none of them cross-shopped with a Corvette. Some of them previously owned Corvettes (mostly Z-06s) but wanted to get something more exotic, refined, and with better build quality. Before I ordered my NSX back in August 2019, I considered the new C8...for all of 10 seconds because there is a lot of bang for the buck, but I didn't want to have a car that would be mass produced to the tune of 35K cars per year and have a rear end that looks like a Camaro. There's definitely no denying that the C8 will be a success and will appeal to the masses, but you won't be seeing a Ferrari owner going to trade in his 488 for a new C8.
People looking to purchase a new NSX are going to cross-shop with cars like a 911, R8, McLaren 540c (in other countries), McLaren 570S/GT, Nissan GT-R, etc. People that can afford to spend $140K+ on a car are looking for something a bit more rare than a Corvette. I did seriously consider a Porsche 911 and an Audi R8, but eventually settled on the NSX because of the underlying technology, build-quality, reliability, and every day drivability. Porsche 911s, unfortunately, are a little too common and suffer from a certain stigma of the driver's being stuck-up that I didn't want have. Many people that see a 911 don't know the difference between a Carrera, GTS, Turbo, etc. It's almost like a Corvette where you can get a Grand Sport that looks like a Z-06, but even people with untrained eyes won't know the difference between a base Corvette, a Grand Sport, or a Z-06. Don't get me wrong, I think Porsche makes some awesome machines, and I would love to have a 911 GT2 RS to play with.
Bottom line is that I don't think the C8 will make a dramatic dent in new NSX sales, and I don't think it will have a significant impact on used NSX pricing either unless people start to get desperate to unload their cars. I would hope, however, that those people won't be in any financial difficulty that would force them to unload their cars at rock-bottom prices.