I get that DL crews traditionally did not use bev carts in first whereas NWA crews did. But after the merger I would expect there to be an adherence to doing it one way or the other across the fleet. However it isn't the case. for the most part the ex-nwa crews are still doing carts and the ex-original DL crews are not.

Has there been a decision on an official standard going forward and if so when will it be implemented?

It's just bizarre. Same thing goes for the giving the passengers the full soda can alongside the glass (NWA style) versus just filling the glass (DL style).