I booked a couple of reservations when I was Platinum Pro and selected main cabin extra seats. I then lost my status, but the seat assignments stuck. There was even a change from a 772 to an a321 on one of the flights, and I was still reassigned a main cabin extra seat despite not having status. I was given an exit row window. I, of course, cannot change the assignment, but I still have it. My suggestion to you would be to make as many bookings as you know you will need now so that you can get the main cabin extra seats locked in.