In my past experience, renewals and upgrades are handled at different times. The first round will be to confirm the number of seats you want to renew. A few months later, they will send upgrade information. Based on priority points levels, they will assign upgrade periods similar to the ticket assignment process last year. During your time, you can choose to affirm your current seats or select any seats that are currently open. There is no chance to end up with less desireable seats, unless you miss deadlines. I am not sure how they will handle requests for additional seats.