@stl156 - Yes it is possible to max out race car aerodynamics, but I doubt that we will ever see this happen with a driver in the car.
And to answer your question I would have to say that there are many scientists and mathematicians that can do calculations to figure out the maximum speed of the race car without having to do a simulation.
Granted I do agree with you once you take safety out of the equation it is entirely possible for the car to go ridiculously fast and I do wonder what the speed could be before it would go airborne.
On the other hand the cars as they are designed now are designed with both safety in mind and maximum speed. I cannot imagine the cars going a whole lot faster before the race car aerodynamics max out and they simply become airborne because they are going too fast.
The cars are designed to go a maximum speed now and in order for them to go faster, even with safety taken out of the equation, they probably have to redesign the cars in order to make them go a whole lot faster.