Well, we could all agree that someone had to create a full on double decker one day and they did. Has it been a success like the 747 in its time? No. Will we see more orders of the aircraft in the future? Yes but not at the 747's rate. Why? Learn from history. When the 747 first came out, Boeing was about to scrap the whole thing altogether before the boom of 747 cargo and flight ops to come.
I feel Airbus needs a NEO a380 and make the plane more efficient AND add more pax/cargo load. A huge stretch but unless this happens even EK will bow out future orders.
Speaking of stretch, Boeing doesn't need to worry about continuing its 747 program or compete with the A380 at all, they have the best twin in the 777X coming up. Make a stretch and worse comes to worse you'll lose the odd 50-100 orders the a380 will get if you don't make a 4 engine.
I heard Boeing will end the 737 program after the MAX (might be another decade and some), most likely Airbus will as well with the a320 then. It feels like the a310/757 will make a comeback and i wouldn't be surprised if after 10 years, we see Boeing announce a new air-frame 737/757 variant and Airbus the same with their a320/a321.
The market so far has been 737/787/777 and /a320/a321a350...sooner or later the airlines would want a stretch/efficient a321/757 to give added range and a more capacity to airlines who don't need a 777/a350 but want something more than a 737/a320.
All in all, its a great time in the industry looking ahead!
