Wow, I don't know how I'd feel about that if they ever were to actually do it.
On one hand, I love Spaceship Earth as it is. Very cool ride, love Judy Densch as the narrator. It's on the high end of my favorites list of rides. I'd really hate to see it go.
On the other hand, it sure would make a great format for something based on the Death Star. While I'm not a Star Wars junkie by any stretch, I enjoyed the movie series, especially the older ones. I can see the ride being a slow tour through it where lasers are firing all around you, ships flying around, etc... That would be really cool.
If I'm forced to pick one, I'd say keep it as is, but I can definitely envision a cool Star Wars themed ride in there.