Opinions are all over the place. One thing is clear fact: In the owners manual and service manual, Honda recommends that the timing belt on a '97-05 NSX be changed every 105K miles or 7 years, whichever comes first (and, on a '91-96, 90K miles or 6 years). If you choose to go beyond their recommendation, well, it's your car, you can do whatever you want with it. But
how far past that are you willing to go? Is anything going to happen if you go an extra year, to 8 years? Probably not. But 10 years or more... gosh.
Timing belts are made of rubber, and degrade over time. The risk you're taking is that the timing belt fails, and if it does, you're probably looking at rebuilding or replacing the engine, and that's likely to cost upwards of $10K. Plus, it's going to break down somewhere out on the road, at a place and time that will almost certainly represent a big inconvenience, on top of that huge cost. Heck, that's the whole purpose of preventive maintenance - to take care of the car, to prevent breakdowns and the higher cost of fixing something after it fails. That's not a risk I want to take. But if you're willing to accept that risk - and the possibility that your timing belt fails and you're then kicking yourself because all those people were telling you to replace it and suddenly you're looking at a huge repair bill that could have been avoided if you had followed that advice - then by all means go for it. I wouldn't.
Also note that you're really not saving a whole lot by taking on that risk. If a timing belt replacement costs $1750, if you do it once every seven years as recommended, it costs you $250 a year, spread over that time. If you do it once every 10 years, it costs you $175 a year. So you're taking on the risk of a breakdown and a $10K+ repair in order to save $75 a year on maintenance. So there isn't much to be gained by deferring maintenance, and a lot to be lost. But again, it's your car, your decision.
Going back to the original question, beyond the timing belt, I would recommend doing all the scheduled maintenance that is due (according to the schedule in the owners manual), and not any services that have been done and whose recommended interval between services hasn't expired yet. If you had to do all of the scheduled maintenance, including not only the timing belt and water pump but also all the fluids and filters (engine oil, transmission, brakes, coolant), valve adjustment, spark plugs, etc, you're probably looking at around $1000-1500 on top of the cost of the timing belt. You might also consider the cooling system hoses at this time - all 22 (I think) or, at a minimum, the two big ones. (This won't add much to the overall bill.)
It's a good idea to have all this work done by a mechanic with extensive NSX experience - not only so it can be done properly, but also so that he can look the car over thoroughly, including any potential NSX trouble spots. The tragic loss of Steve Gooding may leave few options in your area. If there's a great NSX mechanic near the seller or en route, you might consider arranging for the service to be done there.