No, you would not lose your round 1 seat until you are upgraded to a more preferred seat of your choice. This means that once you have got a seat in round 1, it will continue to be your seat. However, you have the option to freeze your seat. If you do not freeze your seat in round 1 and you get a better seat in the next rounds, you will automatically be upgraded to that seat and you can not go back to your round 1 seat.