We may get a better idea after D23. They'll probably announce the Epcot reimagineering and we'll see if they have any plan for the building.
I would not think they'd tear down a whole dark ride while also having to spend a lot of money for everything else, so the second floor should be safe. But you never know.
I love that lounge--the cool glass ceiling is the best. I would love it if there would be more lounges other places in the World. Sadly, I have been thinking that the lounge will be gone with all the work at Epcot. I sure hope I'm wrong.