What happens when ceramic coating wears off?
Your car will begin to look like any other car if you let your ceramic coating wear off. You will never find out if you don't let it wear off!
It is a bit like asking, "What happens when my car runs out of petrol?", if you stop off and get some more fuel when the tank is low, you won't ever have to experience it. Likewise, you can get a top-up for your ceramic coating.
Remember, if the manufacturer guarantees is for 7 years, you can bet it will last a fair bit longer than that. And it isn't all going to disappear all at once. It's a coating which will gradually wear away. You can easily put another over the top once it starts to lose some of its lustre.