Yes, but as @lanejudy wrote, there is no financial advantage to doing so. You would only get credit for what you paid for the tickets. So in my mind, it's best to use the tickets for a trip before 12/17, and then purchase an AP for your next trip, unless that wouldn't work well for your upcoming planned visits.
If you had used any days on the ticket, the first day for the AP would revert to the first day you used the ticket, but that does not seem to be a factor in your case.