Since West is being leveled, Construction vehicles are probably going to access it from the Seas side via the access road. Add to the redo of SSE and fountain of nations, I would figure the entire spine being off limits to guests. They would have to build a temporary path via guardians near the east bathrooms and guest relations. Additionally build a larger walkway around Innoventions east by the playground.
A lot of the initial demo prep work will not require rerouting so simple walls will be sufficient for the fall festivals crowd. I would expect the routing described above to start when Mouse Gears and the Umbrella close at the end of the year.