Me thinks they're waiting to see what makes more between Elio and life action Lilo and Stitch to see what direction to take Tomorrowland into once it's number is called after they're done ripping apart Frontierland.
They've done rounds of investment for Fantasyland, now Frontierland, and Tomorrowland is obviously in a spot where it needs the investment.
Sure they can do Adventureland first, or maybe do it alongside Tomorrowland like how they're doing Frontierland with Villains. But something tells me that once the L&S remake sets the box office on fire and prints Stitch money we're gonna see some movement on Tomorrowland or Adventureland, both lands where they can shove that blue critter at!