The statement isn’t that countries will go by 2000; it’s that we have until 2000 to do something about temperature rises which will eventually lead to countries going.
Then the statement is worthless! If any country is every covered in water at any point in the earth's future then it can be proved "correct".
The negative is not even true -- no one can guarantee that no countries will ever be covered in water at any point in the future, even if we had presumably gotten the rising temperatures "under control" twenty years ago.
The negative is not even true -- no one can guarantee that no countries will ever be covered in water at any point in the future, even if we had presumably gotten the rising temperatures "under control" twenty years ago.