Even if the software was built into the car, it wouldn't help. Many people don't use navigation so how would the car know you are heading for a Supercharger? And then it's even more complicated. Even if you have all cars connected, how would the software know how much you want to charge. A driver could charge just the bare minimum to make it to the next charger, another one might be on the exact same way, but wants to have plenty of buffer because they plan a detour. So there i no way to predict how long a car will charge at a station, thus no prediction can be made about the availability to the next few cars coming in.
But as I said before, even if the system would work perfectly, all it would be able to do is tell you in advance, 'sorry you will have to wait 20 min before you can charge there'. Only more stations will solve the root of the problem.