To be honest, I question if WDW actually wants to take the attraction down for the time it will take to do that. For point of comparison,
Disneyland closed its Space Mountain for roughly 2 years give or take when they tore down the track, installed a brand new one complete with the onboard speakers. The most recent lengthy refurb of WDW Space Mountain was about 9 months or so. Maybe they'll feel more willing and able to do once TRON is running, but we'll see. Because yes, I much prefer the smoother Disneyland version that I fit on without trouble.
The dynamics of the average park visitor are so different between the two coasts and that impacts a lot of the decisions, for better and for worse that are made about refurbishments and overhauls.
SAFD: I would like to Spaceship Earth get an update. It feels like it just falls flat at the end after such an interesting buildup. A return to the original Journey Into Imagination would be fun. I remember seeing it on a 1994 visit to Epcot, but only remember it now through the music.