The issue could be that the demanding country may not take proper care of the art. Lets say a third world country demanding return of its treasures now in a british museum. I recall a case where just this happened and the concern raised was that the country asking for its art was less than stable.

In the end though, if the stuff really does belong to another country, then yes, its only right it gets returned regardless of the art eventual end.

Another example that has a similar ring is countries renaming cities and mountains back to their original names. A conquering country often named the conquered lands cities as they pleased. Its good to see this being made right.

T