Let us distinguish what we can think of as possible from what is physical reality.
The physical reality is as follows: A satellite launched into orbit that follows the shape of a hyperbola will free fall; that is, no force is necessary to move it, This satellite will not impact on the earth because its trajectory matches the curvature of the earth. If you were riding on that satellite you would think you were getting further away from earth. The fact is that satellite is only circling the earth forever. The same thing would happen if a satellite were launched into orbit out of the universe instead of the earth. This satellite will free fall but circling the universe. That is why the statement "the universe is finite but boundless."
The possibility of an end of the universe is only in the mind. It is like building a bridge intended to be straight that would link the earth with Venus. The possibility of such a bridge is only in the mind. The physical reality is that that bridge would end at your feet. This is explained by the generalized theory of relativity. The straightest line is curved called geodesic.