The Nats currently have 3 slots left on the 40 man roster, meaning that only three of the seven of the players you think might get called up, could be, because they aren't currently on the 40 man roster. Any player brought up must first be on the major league club's 40 man roster before he can be called up. Personally, I think LHP John Halama could be added to the list of possibles.
The real question is, which players will be added to the 40 man roster, so they could be called up?
Of the players you listed, I think the Nats will wait until next season to start the arbitration clock started on Bray and Zimmerman, the same with Galarraga. I think any players called up are already on the 40 man roster, but we need to keep an eye out to see if the Nats add anyone to it.