I don't think this will change. Yes, they already require an account for the YT app. But if they block access altogether without an account then they also break all youtube links for unregistered users, motivating people to find alternatives for sharing accessible video links online. I doubt Google wants to take that risk.

I hope it won't change. But they can make watching without an account less desirable; less bandwidth, more ads, no access to newly uploaded videos, first 30s. free, etc.