Trading Jimmy is, assuming Brady doesn't fall of a cliff, the only option. As much as I like him, it seems to be the only logical option. The way I see it, this is what you could theoritically do:
1- Trade Jimmy now.
2- Keep him for the year, franchise him and then trade him.
3- Keep him for the year, let him walk at the end of the year.
4- Trade Tom Brady
5- Keep Jimmy, franchise him, keep him in 2018.
2 is a risk, now is probably when is value is at its peak and unless Brady gets hurt/struggles badly, Jimmy won't see the field next year. We also know that THIS year QB class sucks. Is next year's as bad?
3 is stupid asset management, likely won't happen.
4 is blasphemy and has terrible cap implications.
5 is pretty dumb from a cap management perspective and that would likely piss Jimmy off unless they promise him to let Tommy walk after 2018... but why would they if TB12 is still playing at GOAT level? I mean, he will be 42 after 2018 and Father Time is undefeated, but...
I mean, trading him now seems to be the right move.