Throwing out some armchair imagineering.
If the plan is to build Avatar in The Hollywood backlot and bus loop area, then this new land will be very close to Tomorrowland. This could then give Disney an opportunity to connect the two lands, similar to the Hogwarts Express at Universal Florida, with an attraction that transports you from Tomorrowland (Earth) to Pandora. That type of attraction would fit with Tomorrowland's "space port" theming (although it does seem like they are moving away from that theme with rides like Tron at Magic Kingdom).
It doesn't make a ton of sense with the two movies we have now, because they don't dwell on space travel too much (although it is in there). But Jon Landau did say we are going to see a bit more of earth in the 5th movie. So it's possible that space travel becomes a bigger aspect of the series in those films and that is where the storyline for an attraction could come from.
Could be cool