While I like the Tomorrowland here in California, the theme is going to be damaged with the Finding Nemo Submarine Voyage. Regardless of what some people think of Stitch's Great Escape! it has a futuristic theme (space aliens, laser cannons, etc.) and fits in Tomorrowland well. Nemo does not (fish, in case there be those here who have been living in a cave). I'd have liked it better if they'd found a way to link it to Fantasyland instead (kind of like the Indy Speedway at the Magic Kingdom should be linked to Toontown or Fantasyland).
Now as for the Monsters, Inc. attraction, yeah, I don't feel that fits well, but I'll reserve judgment until it opens. Maybe Mike and Sully get thrown into the future or some other odd twist like that. And any stage show in Tomorrowland should really have some kind of futuristic bent, and not just be some silly Cliff's notes version of "Grease for Kids." Regardless, Disney will do what it wants, but I agree it's a shame to lose the Tomorrowland theme. Disney-MGM is a much better location, in my opinion.