1. Almost all of the labour comes from India and Pakistan. The native population is very small. So Dubai is an international city really, and it can't stop being one. The upkeep of everything they built is extremely labour intensive. If the immigrants went away the city would disintegrate back into sand within a few years.
2. The amount of wealth concentrated in such a tiny spot, with no military to protect it, is probably not sustainable. Just judging by the amount of effort that went into protecting castles in Europe. This place will get raided eventually.
3. Only the wealthiest of the wealthy can afford a home with a backyard in Dubai. So if you have one, appreciate it.
Isn't most of the wealth in stuff like real estate and finance? Those are pretty hard to raid with an army.