Patrick Mahomes, halfway through the 2020 season, has 1,383 career passing attempts. To be ranked on the 'career' record list in the NFL a passer must have 1,500 attempts.
He should hit that milestone during the Denver game - outside shot at the prior game in Tampa if everybody starts deciding to stop the KC run game.
I'm not sure how many lists he'll be #1 on after that - but career rating is virtually in the bag. The current leader is Aaron Rodgers at 102.8. Per Pro Football Focus, Mahomes is 110.1.