Nobody can accuse Dubai of thinking small. The new airport, rendered in the link below, is supposed to exceed the current leader in cargo traffic (Memphis) by 3x, exceed the current leader in passenger traffic (ATL) by 30%, and have 6 parallel runways.
There are two points to make. First, the notion of central hubbing might work well for freight, but it is increasingly obsolete for international passenger travel (although practical for regional/local). The hub-and-spoke system is more costly for airlines and less desirable for customers. Sales orders for the new 787 (and the dearth of orders for the A-380) are evidence that airlines are investing more in smaller long-haul airplanes, anticipating routes between lesser cities (Pittsburgh-Glasgow, Orlando-Prague, etc.). I don't think this grand hub idea is the future and Dubai might find itself with more runway and gate capacity than it can ever hope to fill. Luckily, in the desert there won't be the embarrassing eyesore of grass growing through cracks in the cement.
Second, check out the picture. Anything strike you as strange? Why, in a country that is for all purposes an empty wasteland outside of its urban cores, does there need to be such dense housing right next to the airport? Daytime might be ok for noise, as people work. And, of course, those people need a place to live (Chep Lap Kok is surrounded by high density housing for people working at the airport and its attendant operations). But nighttime is when the freight traffic starts going (anyone who lives in Memphis, Newark or Louisville knows this). Noise will be a problem 24-hours there, and there will apparently be a big audience for it (cargo carriers are notorious for buying older airplanes not used for passenger traffic - planes that have old engines that make no pretension to abate noise...747-200s, DC-10s, and 727s.)
I realize that less dense development costs much more, as city infrastructure like water, etc. needs to be more far-flung. But come on - they have space, and goodness knows enough money...