While many top NFL free agents have signed deals this offseason, players such as Cam Newton and Jadeveon Clowney still don't have teams for the 2020 season. And it's possible they'll only sign one-year deals before testing the market again in 2021.
Even if that doesn't happen, there will likely be some talented players on the free-agent market next year, some of whom could change teams. Of course, there's also a lot of time between now and the 2021 free-agency period, so players could sign extensions that keep them from becoming available.