This was one of my favorite attractions at Disney World too! The last time I was there was in 2000, and they had it open for guests only at select times (re: hardly at all). I hope that they don't get rid of it, but just continue updating it as needed. Maybe as more time goes by, add in more eras.
Along these same lines, here are some links commemorating past attractions that have been replaced.
I sorely miss "If You Had Wings". I'm so glad they still have the Electric Light Parade though! That song is forever intwined in my childhood memories.