We already are to some extent. Zero Rating, which some consider only a cousin of Net Neutrality (though I wouldn't), has not been eliminated under EU guidelines, it's up the member states to regulate there.
In my country (Portugal), the state cozy ISP is already selling new plans where you use an app (!) to choose what 5 apps you'll be given an extra 10GB of data to use on. My Telecom (not the same), for example, texts every other month to remind me I have an extra 5 GB to use on Youtube alone and that Spotify/Facebook/Instagram/Snapchat/WhatsApp is free. And of those, Spotify's paying for the privilege I think, they were really keen on me what I thought of Spotify's promotion when I took their survey, and only tangentially asked about the other platforms.