It's unfortunate that the O.P. used the word "layer" in his query, since this problem has NOTHING to do with layers, frozen or otherwise.
He's asking "how can I show ONLY the isolated OBJECTS (not layers) in a viewport view?" I've got the same issue: I want to show a view of some objects in the 3D model resulting from ISOLATE, and have the view remain unaltered even after I end the isolation in the Model view.
Seems to be no way to do this, which is bizarre, since it would seem to address the main reason for having a 3D model in the first place.