I would need to see some worldwide sales figures before I would believe DIN is slowly replacing yoke, and I don't mean I think it's happening faster.
Where does most diving happen? In warm water vacation locations? Where does most dive gear get purchased? In warm water vacation locations? (training gear and rental gear)
Most new divers buy gear either used by or sold by the instructors and dive shop they are certified by. What type of gear do most dive instructors and dive shops use or sell?
For recreational diving, this is regional IMHO. In Europe most recreational divers may be using DIN, that's what everyone says (I've never been there).
In my months in the Florida Keys, where a great majority of US recreational divers dive, yoke was just as prevalent as I see it here in Hawaii; 99.9%. Once in a couple blue moons someone is asking for DIN tanks or adapters, but I see significantly more European vacation divers with yoke gear.
In tech diving DIN is more popular, but my half way to cave training was completed with a Y-valve and two yoke regs, same as my training buddies gear. (instructor was manifold/DIN/doubles of course)
Not saying your wrong, I just need to see some sales data to believe DIN is replacing yoke!