As I was watching the episode, I assumed they were planning to do something at the end of five years--although I can't really say what I was thinking they would do at the end of it.

If Topher can make it so that Sierra doesn't suffer from paranoia (which we don't really know that he can, since Priya didn't really), then he should be able to manufacture a paranoia-less facsimile of Priya (whether that would "really" be Priya could be up for debate), I think.

Agreed that forever keeping Priya in a box would be murder, at least under the assumption that the Dollhouse works the way it's supposed to (which of course it doesn't, but Topher and Adelle don't know that).