I was going to ask the same question, and think I have my answer, so thanks

We have booked a package onsite for 2 weeks with the free dining staying from 21st April and so have the 14 day tickets included. However we are now going and staying offsite for 2 weeks this October for 2 weeks. Rather than buy a 14 day ticket for October we were thinking of buying an AP for the extra perks (I am currently doing my calculations!). So reading this, if I am right, we can go in April and using our MBs with the AP connected we can use the AP for that visit, and keep the new MBs with the 14 day ticket for a visit at the end of the year.
Now, I guess I am right in assuming there is no way I can upgrade those 2016 package Ultimate tickets to an AP to start Oct 15? I could kick myself as we were just there in May and we could have upgraded to an AP then, but didn't even think we'd be going back this year!