He's about to sign a 5 or 6 year deal w/ the Saints. He'll be playing next 5 years fa show. He'll avg' at a minimum probably 4400 yards the next three years. That's a minimum. 4th and 5th years, i doubt there's too much of a dropoff but most of it will become gravy. He needs to avg 4200 yards next 5 years to pass marino.
The guy turns 33 in a couple of weeks. I don't see him playing at a high level until he's 38-39. His arm strength isn't that great right now and will only go down with age, but he's managed to make it up with accuracy. Chances are that will decrease as well as it naturally does for players.
Then you have to consider his supporting cast: Will Payton still be there if someone offers him more money? I know Saints fans tend to think they are some elite franchise that everyone wants to be a part of, but reality says otherwise. Whenever Jerry Jones comes to his senses and cans Jason Garrett, you better believe he'll come calling for Payton. Jerry Jones can easily drop $10 mil a year on a coach without hesitation.
We're also assuming that the offensive line will stay intact and continue to give him arguably the best pass protection in the league as well. One guy leaves or gets hurt and that could put an aging quarterback having to run around more or get planted more times than he wants to.
Then there is the issue of keeping a great diverse offensive supporting cast in tow. Will they be able to lockdown their defensive stars, the stud lineman, resign Brees to what will surely be a 8 figure a year contract AND give the offensive weapons like Colston, Meachem, and Graham the big contracts they want?
That's all assuming he doesn't run into any health problems.
Can Brees pass Marino? Sure it's theoretically possible. However, I don't see it happening.