It still comes down to the DAS systems in The Strip Casinos, and the macro sites/DAS at McCarran International. And since Vegas won't be getting LTE 800 for the time being, and 8T8R equipment is up in many locations around the city, then launching LTE & Spark at the same time could be the goal of Sprint at this time.
But even then, I have too many variables just in my scenario. Frankly, it's smart of Sprint not to officially launch Las Vegas until the DAS systems are substantially complete. Besides, most people in Las Vegas know that Sprint LTE is all over the city.