I confirm that if you already own FlightControlReplay v4.5, it is still working, it is still yours, and you can keep doing with it what it’s made for. FCR5 is not a fix for an issue, it’s not a reskin of the same code.
As I wrote earlier, FCR 4.5 has been enhanced over 10 years for one fee, and a small one. Various simulators support have been added at no cost on top of that. I did those upgrades free of charge, already.
You could also notice that existing users do not even pay half of the base price. Think about FSX users who own their tool since 2012. They get FCR5 for 8.25 Euros… that’s like 1 cheap book, 1 dessert in restaurant. Try to see the things from another point of view, you are not “dimed all the time”. You actually chose to use paid products. In my country, if I feel I’m dimed all the time when I’m on the highway, I take the next exit.