I heard Imagination and SE are fighting it out to see who gets into line next. Imagination has a slight edge due to not needing a complex re-track. There's the chance both go down together though.
There's a chance ANOTHER Future World ride could get a redo before either (I heard Mission Space may get something within 5~ years, Living with the Land also, but that'd be a show effects update versus anything drastic) long term goal is to get those two fixed before EPCOT50.
SE current plans look promising. Disney might be trying to court a certain big tech company to sponsor SE to justify a full track+it's costs. (
)