I live in Dubai and I highly doubt the new store would replace the Vox Cinema in the Mall of Emirates. The theater is doing quite well and the location doesn't quite fit either (right next to it is a large food court and the floor below has Virgin Megastore nearby). All of the electronic shops are toward the east side of the Mall, and recently Jumbo Electronics went out of business I think. So that could be the potential new store. Otherwise, I wonder where that "biggest store in the world" could be because Vox Cinema itself isn't even that big.
Another fact to think about is that in the Mall of Emirates there is already an Apple authorized store. I wonder what will happen to that store (although hardly anyone purchases from that store based on what I have seen)
Could it be located in the area of Borders book shop next to the Vox Cinema? That closed down a few weeks ago for renovation and is not due to open until 2015. I passed MOE today on the metro, and it looks like there is some construction going on in that general area on the outside. Maybe that part of the mall is being extended?
Anyway good news if UAE is finally going to get a proper apple store