They've been going back and forth a bit, but I expect that ultimately the 50lbs (23kg) limit will be put in place for all AF/KL/DL/AZ flights. Protect employees, save on fuel, force people to have more bags and fork up the cash... whatever the reasons are, it is what it is.
I sometimes travel on longer trips (several weeks) and I have to pack enough stuff. A carry on is just not an option. I've seldom gone over the 50lbs limit, but I got really good at packing a suitcase and although I never get suitcases larger than 24" I can easily go over 50lbs. All I want to say is, don't judge... not everybody can just use a carry-on; it's often not a choice.
Don't hold your breath, I don't expect there to be an announcement from DL. The only announcements they make nowadays are those that push AMEX.
It baffles me how badly they're failing at this harmonization game, even with the simplest things. Clearly they don't WANT to (no instant profits means DL doesn't care). NW/KL did a splendid job. After all these years the JV is a joke, from a customer's perspective.