The new record would have an * by it and ED's record would live forever.
For awhile.
Roger Maris' record had an asterisk for awhile and then it didn't.
Other 14 game records in the NFL had asterisks when passed in 16 games and then they didn't.
OJ Simpson was the only back to ever do 2000 yards in 14 games, although with all due respect to Dickerson... he was pulled from a number of games leaving a lot of yards on the field. Which is crazy to think of a guy running for 2105 and STILL leaving a bunch of yards on the field, sometimes being pulled in the early 3rd quarter. So yeah, only in Dickerson's case would he have done it in 14 or less if he'd played every down.
But yeah, the asterisk is there to remind people of the change and then it goes away.
Rest assured, if someone runs for 2115 in 17 games, they'll own the "single season rushing record" because it's single season, not "highest yards/game avg over the course of a season".
But yeah, it's still likely to last awhile.