That looks to be very difficult for several reasons:
- The intervening roadway, Buena Vista Drive, is on grade thereby blocking any canal going directly across to Epcot
- Even if they were to find a way past this, where would you enter Epcot? A third gate somewhere behind America?
- There's a circumferential road behind all the World Showcase countries that would also get in the way
- If they instead considered building a canal over to the small body of water outside DHS so that they could then follow the same route as the current Epcot/DHS boats, they also have a problem with the automobile entrance to DHS from Buena Vista Drive near BW.
I'm sure the Imagineers could overcome those obstacles if they wanted to, but I think it much more likely that bus service (which would be needed for the MK and AK anyway) is the expedient way to resolve the transportation question.