Then yes I think in the future retrofitting Tom Sawyer Island into an expansion pad would be needed.
I agree!
But at the same time I think filling it in would create more of a concrete jungle which I wouldn't want to see at MK
I think it wouldn't be that bad depending on how it's done....
It could use the Rivers of America bridges in "fun" and explosive ways similar to TSI currently, unique barrel bridges and paths and such. Depends on the storyline with the expansion though.