You've been to exactly one rehearsal and you're more focused on where you're sitting and how/when you'll move up than you are with fitting in with the group?
I would imagine the director would like to see you show up more than once and commit to at least one full season before thinking about giving you first or second chair.
Best case scenario for the director is that you'll stay with the group for many years and help build a really strong section. Worst case scenario is that he moves you up and loses the other trumpet(s), then you get bored and quit, leaving the group in a bad spot.
I'd suggest that you build relationships with the director and the other players and see what happens in a few months.