Yes this forum is full of 20+ page discussions on topics that could be covered in a single page. osubuckeyeman and FreeBaGel already addressed the relevant points on page 10. If the Pats trade JG for a 1st and a 4th, then that means they don't think he's a franchise QB, plain and simple. This thread will continue to live on for several more pages but that's what it means given all of the variables. Most of the counter arguments are based on Brady starting 3-5 more years for the Pats, which is almost certainly not going to happen. Even Favre only made it to 41. Testaverde and Moon both made it to 44 but their final years were as backups. Brady probably has two good years left. If the Pats believe JG is the guy to replace him, they will move heaven and earth to keep him. If they do trade him, that speaks volumes as to how they view his long term potential.
It's possible that Garoppolo would be a decent downgrade compared to Brady, yet JG could be a significant UPGRADE for other teams. No one has really chimed in as to what a "franchise QB" really means, but if Garoppolo were traded and performed like Alex Smith, Andy Dalton, Ryan Tannehill, Matt Stafford, or Philip Rivers then what? Would that make him a franchise QB? A decent QB on teams that struggled to win, struggled in the post season, or otherwise weren't SB winners?
I really have no idea what people expect Garoppolo to do if he DID take over for Brady. If he went 11-5 instead of 14-2 and went one and done in the playoffs that would be a poor outcome compared to Brady but overall a decent outcome for 31 other teams. If he went to CLE, SF, or CHI and got them to 8-8 . . . is that a success or not really?
As far as Brady goes moving forward, few quarterbacks put up the numbers and the results he put up over his last three seasons at any age, so he is starting higher on the performance scale at an older age already. By that I mean, if his numbers and skills started dropping at a rate similar to other players, he still has plenty of time left to decline to that of an average QB. I know that people will say he will go from the penthouse to the outhouse almost overnight, but he doesn't really show signs of that at this point.
At some point there will be few players to compare him to. People said the same thing about Jerry Rice, that WRs had to pack it in by age 35. People said the same thing about Emmitt Smith, that RB's couldn't be productive past 30 or 31. Brady from ages 37-39 had the highest passer rating out of anyone in the league and won 2 of the last 3 Super Bowls. Of the other guys in the past that played at that age, their production on the field and their team's success wasn't close to that. At some point, people will say Brady is breaking new ground and is not like all the guys that came before him.
Only Brett Favre did anything as a 40 year old at QB (4202/33/7) and only Warren Moon did anything as a 41 year old QB (3678/25/16). IMO, the Patriots would take that type of production and would still be in great position to get back to the Super Bowl. Brady doesn't half to put up giant numbers every week for the Pats to still win consistently. If at age 42, Brady put up 3600/23/12 like he did in 2004 and NE went 14-2 again, would people be saying he was hurting his team?
Let's save the discussion for when things go bad when he actually gets to that point.