So what is VW actually liable for here?
Well, a couple of things.
Everyone who bought a Volkswagen could say Volkswagen are guilty of misrepresentation. In Belgium that would make the contract void. Volkswagen would have to pay back the money and additional damages. Of course few people will go down this route, because that would mean turning in your car. And according to Belgian law you would only get your money back for what the car is worth today.
Another problem is that cars are taxed for their pollution. Because Volkswagen lied about the pollution, the logical consequence would be that that everyone who bought such a car has to pay additional taxes and penalties. Of course they would ask their money back from Volkswagen in this case..
Between all this stuff and the fact that people will certainly consider buying somewhere else in the future, this is going to be a big deal. As far I can understand it may not entirely be justified as there are voices saying that other car companies are just as bad.