Not sure if it was used again in the past 10 years or so, but the two times I remember experiencing it was 2007's Dead Silence & 2008's Interstellar Terror
The only two images I was able to dig up:
View attachment 20863
2007's Dead Silence "catwalk" scene is where you'd encounter the dropping floor. Thanks to the mirror it gave the illusion you were high above the stage. What you're actually seeing is the reflection of a Mary Shaw dummy upside-down several feet up. It was a great effect & memorable!
View attachment 20864
2008's Interstellar Terror "explosion" scene is where you'd encounter the dropping floor. I believe this image is of that scene, but it's hard to tell without the show lighting/effects. You'd pass through the spinning vortex tunnel of doom & you'd come to find that the ship (NSO Columbus 1492) had flipped upside-down. On either side you'd see a domino style effect on the "floor" coming towards you, once it reached that little hub, the floor would drop.
Unfortunately nobody really thought to document the floor where these effects were located. But hope that helps anyone wondering about these two past floor dropping scenes.