As a Pat's fan this is how i think this will play out. Jimmy G's contract is up after the 2017 season. At that point, if Brady doesn't want to retire the Pat's will trade him or cut him and franchise jimmy (or work out an extension).
I love Brady, obviously, but you don't trade a potential franchise guy (Jimmy, and I think he can very good) at age 24, because you have a 39-year old. The hard part, however, is somehow Brady has elevated his game the last 2 years when statistic say he should've declined.
But in 2 years, when Jimmy G's deal is up, he will be 41. So I think that is the year they move on from Brady. There will be some dead money, but they will still save money on the cap that year. They can't cut or trade Brady before that -- even if they wanted to (and they don't-- because he has 28 million in dead money as of now.