Rule to remember: in determining which use year points you are using as "current" use year points and whether you need to bank or borrow, wipe from your mind the day you go online to make the reservation and look only to the dates you will be at WDW. Thus no matter when you make the reservation, for an August 2017 trip, your June 2017 points will be your "current" use year points, if you have June 2016 points you would need to bank those before you try to reserve, and if you need them, you can borrow points from your June 2018 use year when making the reservation.