The stage for Lights Motors Action is about 80 metres wide. World of Color has a 380-foot-long mist screen, which is approximately 115 metres. So yeah, you're right, World of Color is too big to fit into the Lights Motors Action stadium.
Of course, if they scaled World of Color down a bit, and made it 70% smaller, it actually would fit in.
I've never been a huge fan of Lights Motors Action, so to see it replaced by World of Color would be fine by me :-)