Those are all options. Which ones are available to you will depend on the current climate. If you don't get the one slot, you could do another tour. If the Army needs more neurosurgeons than it can train in its programs then you may get a civilian deferment (though I know for USUHS grads this is not an option). These are all maybes and you will get a sense of things when it gets closer to the time. The fact is that you have an Army obligation as a West Point grad - if you want to do medicine then you will be able to fufill that requirement in medicine. As you are already learning there are no guarantees with the Army. You get what you want by being adaptable and planning ahead as best you can. I like to think of it as a controlled fall. You can try to maneuver away from things, but sometimes you can't avoid them. Conversely, you can aim for the nice, soft bushes but you may land on the concrete.
Geo