Not having subs in your preference list doesn't prevent the Navy from assigning subs.Any rumors on how this actually impacts service selection? They have already nicely forced us to put subs on the list by allowing us to put only one SWO option? So are they gonna take less pilots and more NFOs? Or just less in general?
There are always various pendulum swings to correct manning numbers. Just a few years ago, there was a mass exodus of aviation LTs who failed to select and were drummed out. Now we're short. In a couple of years, they'll be an excess that will be corrected via DH screen. Even if you select for aviation, that doesn't guarantee you will make it through Pensacola, or that you'll select for milestone/department head later on with increased numbers and heightened competition.
You can drive yourself crazy trying to calculate the chances. Hope for the best and be prepared to serve as an officer in any community until you're done with your service obligation.