The deal did the following
1) gave Brady $8M over and above his 2019 contracted amount
2) freed up some cap space (it could be use to bring in a player, or more likely, extend a player
3) made Brady a free agent at the end of the season
4) prevents any new contract before the end of the season unless it is a lowball deal
5) prohibited the patriots from franchising or transitioning Brady
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BOTTOM LINE
2019 is settled. Brady is a free agent at the end of the season. While Brady is 90% likely to continue here or retire, any team can contact him at the end of the season.