It does sound like a good upgrade.
There seems to be reasonable emphasis on the 4D part. It will be interesting to see what new 4D effects are used that haven't already been tried (Muppets/Bug's). Now that every WDW park has a 3D show it will probably be the last new one they make for awhile. This one seems like a natural for exporting into the other parks, so hopefully they did it right the first time.
If the JIYI rehab turns out half decent, there could once again be a reasonable slate of new things to experience for the 2003 visitor.