Wait, "closed indefinitely" does not always mean "closed forever".
The fountain is probably going through some renovations. When we were there last August, we noticed that some of the air jets were not working as they used to and we saw one of the air hoses flying around loose in the fountain. It was "fixed" the next day, but I am sure they need to do some work on the whole thing.
The fountain is a pretty popular part of that area of Epcot, I doubt they would just fill it in.
Ted