I'm pretty sure once the team season is over with... It's immediately the off-season and they can makes moves to cut or extend players. Even though most players like to wait till FA period to do it.
I think you have to wait until a few days after the Super Bowl when the new league year starts for it to count on next year's cap. They also may decide to wait until they can designate him a June 2nd cut so that they can split the dead money over two seasons.