My thought is that Dubai striking back is likely. Since the Burj Khalifa had the literal advertisement / showcase of "Expo 2020" on the building in videos for the New Year's fireworks, it seems almost certain that they'll be proposing another grand tower soon.
But while they could build the tallest commercial tower (which is fine and all and is it's own record), if they wanted to go for a WTB again, we'll need to see it and soon if there's any hope for completion around 2020.
I'm sure they went to the drawing boards as soon as they had word that Kingdom Tower was a serious proposal / contender for real construction without delay. But if it's 2015 now, figure designs will take the rest of the year to be finished. One year minimum for foundation work, two years minimum for superstructure, and a year and change for interior work pushes this conceptual thought already to mid to late 2019.
Unless planning and things are already well underway, it would be a miracle to see a WTB topping KT by 2020. But again this is Dubai, and records can take many forms so we can only wait and see what, if anything, is proposed.
Maybe they'll just hold this Expo akin to a major convention in any other city without much pomp and circumstance but that would seem.... unlikely.
Does Expo 2020 even have anything to do with architecture?
At any rate back on topic, it's nice to see Kingdom Tower hauling along now. They're appearing to be more or less on schedule and as the floorplates slowly size down and the floors become a little more standardized, the construction speed should increase.
