Pretty tricky to route an expansion from the east side of Studios to go westward. You can go to All-Star with one turn. You can go north with one turn to go west to Coronado Springs. They would not build a line for park-to-park transfer, that's not a steady stream of people. They want to move people to/from resorts and parks.
I cannot imagine ever considering a line to Disney Springs. Bad enough people park there and get on the buses to the resorts to go into the parks and avoid parking charges. A line to a park? Abuse city.
If they were ever thinking to expand from Studios, they left no room to add additional lines next to the Skyliner station. They recently redid that parking lot and you think they would have left space.
I imagine electric buses is their plan for moving people from now on.
Imagine this: I've wished for a light rail line (like those at many airports) from the TTC heading south, curving past Coronado, Animal Kingdom, All-Stars, and ending at Studios. That would eliminate many buses and could run late for getting to resort restaurants, and be far more resistant to storms. I'd love to see another line from EPCOT to Port Orleans, OKW and Saratoga Springs but there is a golf courses in the way!