For any potential merger, first you'd need to get past the egos and willy waving about EK having the stronger brand and EY having the cash (well the AD govt having the cash - EY has basically been a cash furnace) and all the machinations of what it would be called - United Emirates?
The next issue is simply one of logistics in that Dubai and Abu Dhabi airports are still a relatively long way from each other. Would AD pax want to drive to Dubai to fly to Paris, or New York? Or would Dubai pax want to have to schlep to AD to fly to Manila? There would still be a lot of replication at each hub. You could shift all the DXB flying to DWC to move things closer to AD but it's still well over an hour to downtown from there, as well as being less convenient for DXB pax.
Smarter minds than mine would have to figure out how the flying program would work with two hubs so far apart. One option would be to have say a DXB-AUH-LHR or CDG-AUH-DXB routing that loops in both hubs but flying widebodies on short hops like this is horribly inefficient. Not to mention that it would be impossible to tag an additional AUH rotation on the end of a LAX-DXB sector without a fresh crew. Shhh, I shouldn't give them ideas.