Ill say this, if they come out of preseason feeling good about Thorson or even DiNucci to keep them on the roster, Id be open to moving Dalton if the opportunity arose.
You definitely arent getting a 3rd like OP suggests, but I'd be happy adding another 5th. All of this unlikely. The stars really have to align. You need a another QB to emerge as someone you feel comfortable with, and you need a team that comes into a sudden need for a QB starting experience. What makes it less likely is that Dalton would have to learn a new system in season. Remember when we had to start Weeden because Cassel wasnt ready