Is it possible to create a 3D firework show?

I thought they already were. Are you talking about like an iMax 3D fireworks show?

How are fireworks not already 3D?

Well I never seen like a firework cube or pyramid,... I seen only like numbers for new years like 2009 .

If you are looking for “true 3D” you will not find it. In order to see 3D you need parallax or a difference in view point from your left and right eyes. Your eye spacing is so close together in comparison with the distance to the fireworks you get the same effect if you watched them with one eye.
Patterned fireworks available that make Saturn rings, or Smiley faces but, in general, the burst will always be spherical.