I can't help to think that we will -one day, probably soon- have enough 3D face models to just replace those in these movies with some that will fit the original version.

The resulting faces won't be an exact match due to the low quality of the original, but unless you knew these people, no-one will be able to tell.

Same with pretty much every other aspect of the scene: have good models that fit the original scene and re-create a full 3D version of the whole movie, at any level of definition.

Once this process can be automated, we'll be able to recreate all the classics, shot for shot.