Based on my many visits to many different Acura dealerships, it seems like each Acura dealership is completely different in philosophy and operation than the next. So I wouldn't take anything as gospel based on a single Acura dealership doing something. His Acura dealer may suck, financially strapped, etc., who knows.
There is no way these are going for under $100k in a year, or even in 2-3 years unless they are abused or had a hard life. The very limited supply of these means they are not going to depreciate that much. However, other market factors could cause them to drop, such as a dip in the economy, Acura coming out with a cheaper / stripped model, or Acura flooding the market with NSXs if they do not stick to "custom order only for 2018's and later" model.
Life is short, these are amazing deals. You can always wait a year for prices to go down. At what point do you stop waiting and bite? It might be too late at that point.
PS - is your friend serious about selling his NSX? If so PM me, seriously interested, I'll beat all dealer offers.