I'm a fed and I do a lot of hiring for my department. I also think it's appropriate to mention the promotion, but be prepared if they tell you that they still aren't in a position to make a decision yet (which can be for any variety of reasons.) More than once, I've had my first choice come back and say that they have another offer. If I know we can't make a quick decision, I wish them the best and ask them to stay in touch. If we really are close, then I can push it along.