Wouldn't be a bit surprised about the one-year deals, even though it's a pretty big risk for a top player to take.
I think with the reduced cap, that might be some veterans only option. A year or more ago most teams were assuming and planning for an increase in the 2021 cap, not a decrease, so when contracts were being drawn up, they had a much higher 2021 cap in mind. That will leave some teams scrambling to even meet the cap, some teams will be on a tight budget and a lucky few will still have cap space to snag some of the free agents that hit the market. I also don't think the Free agent market is going to be just those players with expiring contracts, we are going to see players that teams just can't afford due to the lower cap, so they cut them.
All that said, its basic supply and demand economics. The supply of players will be up and the demand or at least the ability to spend will be down. Packers Russ Ball is going to have to be very creative with contracts and try to push the cap hits of current and new players out beyond 2021, but you can only do so much of that, before you have over leveraged your future. Needless to say, this is going to be one interesting offseason, after the Packers win the Super Bowl.