Incredible Drone Display is World’s Biggest Ever - Guinness World Records - YouTube
Just to be clear, the noise and air pollution that a switch to drone shows away from fireworks shows would save, would be incredibly significant. I don't think the cost makes it viable yet, but it's something to aim for.
Looking at the beatiful show, I cannot avoid thinking: "each of them a potential weapon".
So in fair weather, when communication is smooth and all navigation systems are working, it's entirely feasible to coordinate a swarm of 10 000. Wow. :)
Soon enough, they will be coordinating each other in the presence of electronic warfare, and swarms of 100+ fly already, so 1000 is the next step. Anyone doing air defense is probably designing energy weapons (lasers, masers, etc) at a pace approaching madness, besides making ever-cheaper drones.
As for the environmental footprint - if each drone withstands 10 performances, they will probably save resources. :)