We went the first 2 weeks in June & really didn't notice much of a change from our last trip in December of 2000. When we went in April of 1999, Mr. Toad/Pooh's New Ride was being "refurbished", & Horizons at Epcot was being torn down (

).
This past trip, the new Aladdins Magic Carpet ride was up and running (Yeah!!) (which was under construction when we went in 12/00.) The "who wants to be a millionaire" was open at MGM. The new "journey into imagination" open at Epcot.
In the last 2 trips we have also noticed they have opened Ariel's Grotto, Buzz Lightyears Space Ranger Spin, & Playhouse Disney Show at MGM, & Several at Animal Kingdom.
When we went June, The Great Movie Ride was open and Carousel of Progress was open from 11 am to 5 pm. (You must of hit them in "refurbishment stage") (On our trip in 1994, we hit Spaceship Earth during refurbishment....what a bummer!) I would be upset if I missed The Great Movie Ride on my trip, I always do that ride twice!
I don't know of any rides that are currently on there way out the door, but I do know that the new space ride (Mission to Mars)that took Horizons place (

) will be opening in 2003.
Also, I think they closed down River Country....not positive though. Maybe Mickey can confirm this for us.
As far as closures, I have not heard of any. I couldn't imagine ANY in the Magic Kingdom...every ride is a classic.
I hope things keep changing for the better!