Sounds to me like they are stringing you along as a Plan B. I could be wrong, but so far the parents that I have dealt with that want that spot when they come back are very clear about it.
Her vagueness, the fact that they have moved, etc says to me that they will probably not be back.
As I said before, I would get something in writing before terminating your other family. For everyone's sake!
Good luck!~![]()