Many share your concerns it seems.
I’m not saying they’re invalid.
I think this 1 November rule more than a year before the season in question is mis-leading. Many seem to think a whole bunch of signings should/will be announced immediately. I haven’t seen any (I think) but certainly not many announcements from any club regarding 2021 recruitments from other clubs.
I also think what makes it worse for the Dogs in 2020 is if a 2021 announcement were made today, many clubs seem happy to cut the player loose immediately and we have limited cap room for 2020 and quite likely can’t accommodate them. On that basis, you make the 2021 announcement later.
The other thing is that mid-season transfers are becoming more common. Better than average chance that players will become available in 2020 that aren’t currently on the market.
Finally - we will undoubtedly let a bunch of players go at the end of 2020, open spots for 2021. Whilst some of those names may have already been decided, several are probably not and are waiting on 2020 performances to decide. Many will be playing for a contract in 2020 - let’s not jump the gun and see how they go...