Even 90mph is plenty fast. The key is reliability. If people can count on the train showing up on time and delivering them on time without complications, they will use it. Equally important is frequency of service, because having just one train go by each day at a really inconvenient time drives down usage.
Consider the Amtrak route across the Northern Plains. It's reliable, and even though it only runs once a day it's packed. The alternative is driving for miles and miles across the plains in whatever the weather.
Actually higher speeds are an impediment in my book. The freight railroads barely tolerate 90mph track because they have to have cab signals leading all their trains. The higher speed means that they wear the track faster, particularly in the curves, because the track will be banked for comfortable passenger service. The freight traffic at 60 or 70mph will lean in too far and cause excessive wear on the inside rail. They won't even touch 110mph track, so you have to have extra tracks just for passenger in that case.
I think it's great we're still talking about this option. Patrick Simmons has been working tirelessly on this project for a long time. However, we're never going to see federal funding. We can't even keep the interstate system in repair anymore. NC and VA are going to have to spring for this all by themselves.
Also, don't expect passenger rail to make any profit. It never did, except in a very few rarified instances, and only when you ignored the big picture, and only in the heyday of passenger rail before 1960. However, for all the times I've heard the words "money-losing" flung at Amtrak, it still does quite well. The system fare recovery rate is 80%, which is far better than almost any other mass transit entity, especially in the US. Imagine how well they could do without always being starved of capital?