Iirc at T-72 hours what's called 'Theoretical Seating' kicks in. This means that you'll only have a choice of a small handful of seats, as all the rest are blocked, but once those available ones have been chosen by others, then more blocked but not occupied seats will open up, and so on until everyone has a seat. The order of unblocking seats is based on who is sat in the adjacent seats, so seats next to Blues and Bronzes will open up first, then seats next to silvers, and the last to open will be seats next to golds.

Basically, you have nothing to worry about, but as theoretical seating has started, you will have a limited choice of seats when you check in at T-24, but you will have a seat.