Don't count on Disney replacing the attraction with anything in the short term....
Christ, look how long the lagoon has remained untouched. Just because they close something, it doesn't mean it will be replaced with anything.
If attendance was as bad as reported, then closing Timekeeper should have no effect on the rest of tomorrow land which would require a new attraction.
My guess, if Timekeeper went down for rehab, this is all a moot point. If not, don't plan on ANYTHING going in for at least a few years.