There is expansion built into the EPCOT station footprint.
The Studios alignment you're talking about has been looked at multiple times over the years - it's the generally accepted alignment to Studios if this is ever to be built, although Soarin's in the way now and there would need to be a minor reroute. In the late 90s, one of the more recent serious looks at transportation on the property had this alignment from the EPCOT station expansion pad going by Seas through the gap between Imagination and Land (where the Soarin' show building is now) over to Studios, with a possible station pad for Yacht/Beach/BW/Swan/Dolphin and a likely continuation to Animal Kingdom. The company has also looked at utilizing light rail and other options.
Each new look takes the current needs of the property into account, and that changes, depending on what's being built, budgets, annual guest counts, who the current transpo execs are, governmental regulation, etc. I wouldn't take anything for granted until the permits are filed.
I'll add a bit on the thinking behind the planned-for expansion at the time, and how that ties to the EPCOT spur line that was incorporated into the blueprints for future expansion. In the early 70s, the company had grand plans for the Walt Disney World Village/LBV, including commercial space, residential, shopping and hotels, with multiple internal transportation modes, including scaled down monorail and PeopleMovers. There was still somewhat of a central plan to the property build out, centered around the intent that the FL property be a place where corporates, academia and government could come together to discuss problems of the day. (Something Walt supposedly passed down to the execs who knew him, including Nunis, Walker and Miller.) The thought was recreation was first (Magic Kingdom), then the community (Village) and the Center (EPCOT). All were to be linked by internal transportation, which at the time had monorail and PeopleMovers at the forefront. The expansion of the Walt Disney World Village was put on hold when EPCOT went forward. The footers for the spur line were poured within the confines of the construction zone, as was prudent, since they were already pouring them for the loop. There were no footers poured on the west side, as there was no need. Construction also lost a few of the piers to the soft lake-bed by Odyssey. When EPCOT was completed, after many rounds of changes, there was a plan in place for a large expansion to the Village, with a full New Orleans street section leading from the Empress Lilly to a New Orleans themed resort, including new shopping, dining and entertainment, plus expansion of the conference center and the treehouse villa condos. The plan in the fall of 1982 included a 2 mile double beam from EPCOT to the Village, with a new station at the Village. The Village was looked at quite differently back then, though, and the expansion of the monorail was considered a big marketing point. Then management changed, and all of the expansion plans changed with it.