What happens if you obtain A-List or A-List Preferred when you already have future flights booked?

For instance, I will be hitting A-List Preferred in a few weeks, but I already have several more flights booked later this year. Will they somehow automagically upgrade to A-List Preferred and update my boarding position?

I ask because I've seen a few discussions that say that your A-List or A-List Preferred boarding position is determined by when you bought the ticket. So right now those tickets are just assigned regular A-List positions... wondering if they will backdate and become A-List Preferred even if other A-List Preferred people have booked more recently (since technically mine was booked earlier), or if it will just add my bookings behind the more recent A-List Preferred bookings (since after all I just got the status) but in front of regular A-List bookings (where I would have been originally).