Speak to any follower of the Void God, the great Kyloth, and they will tell you this: High Realm is doomed to be consumed. At its heart slumbers the Void God, and when the world at last has fulfilled its purpose, Kyloth shall rise from his dark prison and flood the land. He shall end all light, all song, all life.
Ask this same follower what the purpose of the world is, and they shall answer:
The world exists only to die.
Which is either a very roundabout way of saying the world will never die, or the followers of Kyloth have no idea what they are talking about.
But one thing of note is that the Realms, the Spheres, and the Cosmosphere itself are in constant motion and change. Who is to say that one day they shall collide, collapse, or be consumed by some other force that cannot be known?