The article said the roster spots will be freed up while the players are on IR. They'll be allowed to sign replacements, no one will have to forfeit from lack of players.
I wish they'd allow the full 90 players (from before cuts) to still be on payroll, even if on a minimal payroll. Still tethered. At least that way, one has known backups - guys that went through camp, learned the playbook, got the reps in. But this IR solution is a cheaper solution, so it happens.