Let me start with last one, since I was thinking/posting about it recently on main board (unfortunately the thread was hijacked by crazyAndy.. again..) I am happy to have peaceful discussion here.
I don't think anyone knows incl. TB & BB. But i can see everyone (except the fans of course) is prepared for the no option.
What I do know is that 40 is a funny age when body and mind start to go down regardless. Everybody's telling me the same story I experienced myself. It can be little things like eyesight going down by 10% etc. but they affect performance. They affect it invisibly and thats the hardest thing. Brain starts working slower by invisible margin and that can be a big difference in QBs game.
Brady's approaching that border. And even if he crosses that border better than most - there are other (personal) borders he is aware of.
Sorry for these elusive thoughts. I can see him starting in 2018. Current contract would suggest Pats see that too. Beyond that Id be surprised.
And that brings me to the more important and slightly less speculative thoughts: how are the Pats prepared for this complex situation. The answer I was coming to in some of my recent posts suggests - best they could be. They are in such a good cap and roster shape at the moment that they could even swallow worst case 2018 cap scenario of carrying both QBs on their top cap hits - 45M combined. (more about this in next post)
I don't think that will be necessary because TB and JG share the same agent that works very well with Pats FO. If needed they can asses situation daily and act accordingly to lessen cap burden if needed.
Keeping Garoppolo this season (or at least offseason) against most people's beliefs could hint the decision being made - but not necessarily. It could just as easy be only about 2017 & best insurance for almost no cost. But every day that passes with Jimmy on the roster the closer we are to the change of reign.
Lombardi and Schefter believe Pats have their future QB on the roster in Garoppolo. If that is true than Brady is retiring within two years time.