It will be interesting to see how story driven this transition will be. Part of the magic and power or a world is it's reveal. It's magical appearance or transformation or gradual dissolve from one place to another. Disney parks borrow from the "cross dissolve" in films where each world softly fades over the other with a neutral ground in the middle. We usually use landscaping that is common to both worlds as a bridge and the music fades in and out. Sometimes a portal does this as it does in DL Toontown or the MSUSA RR Station at Disneyland. This is a "fade to black/fade in" type transition. "Dissolves" usually happen in movies because the change if edited directly (smash cut) would be too jarring, so in that respect, so can a land if the premise changes. Tomorrowland just happens, you don't have to take a "Time Machine" to get there, the transition does that, although I'd love that to be one way to arrive.
FWIW, i'd like to see a ride that reveals in a story then dramatically ends in Pandora and you get off the ship and explore it yourself like a Tom Sawyer Island experience, filled with interactives and maybe even other rides. Like Kevin's description, (i.e. the indoor Mermaid area at TDS), it's a ride feeding an indoor land. If you did not want to do the ride, maybe you can enter another way so this is not forced on you, but I would love to see someone do that right. This has not been done because there is the argument that the capacity of the ride limits the land or it's going down, but you could have more than one way to get there.
We tried to make the JC take you to Indy at DL, dropping you off at the distant Temple in the Jungle (African Veldt) with a footpath back, that way if the JC went down or you need to meet someone there, etc. you could.
