If the GDPR is any indication, WhatsApp could just choose to stop offering its services in the EU.
WhatsApp is already DOA in my circle of friends, it might come back but the odds aren’t great.
Getting out of the EU would be a massive blow to any established social media company that depends on network effects. It doesn't matter as much for smaller companies that are still growing (eg. early Facebook still managed to grow by only offering services to college students).