Inside the Article:
Following the conclusion of the 2022 NFL regular season, it sounded like Detroit Lions offensive coordinator Ben Johson would be moving on to bigger and better things. But after interviewing for a couple of head coaching positions, Johnson announced that he had made the decision to stick around with the Lions. The Lions gave Johnson a substantial raise to stick around, but that does not mean he will stay forever. With that being said, there are a few internal candidates the Lions would consider to replace Johnson if he ends up taking a head coaching job following the 2023 season.

3 Detroit Lions internal candidates to eventually replace Ben Johnson
If Johnson does move on following the upcoming season, I believe the team would consider Tanner Engstrand, Scottie Montgomery, and Mark Brunell as potential replacements.
Tanner Engstrand
If Johnson jumps ship following the 2023 season, my belief is that Tanner Engstrand would be the favorite to be his successor. Back in February, I wrote an article about the Lions possibly already having Ben Johnson 2.0, and though that may be a stretch, I think he would be the ideal replacement.
Scottie Montgomery
Scottie Montgomery is a well-respected coach, which is why Dan Campbell went out and hired him as the Lions' assistant head coach and running backs coach. Montgomery would also be a logical choice to replace Johnson, but there is also a solid chance that he lands a head coaching gig following the upcoming season.
Mark Brunell
Brunell, who is the Lions' quarterbacks coach, does not have a ton of coaching experience, but he has clearly formed a strong bond with QB Jared Goff, which puts him in this conversation. Though I put Brunell at No. 3 on this list, I do think Dan Campbell would interview him for the OC position if it becomes available.

Bottom Line: Let's Hope the Evil Genius Stays FOREVER!
The Lions currently have one of the best offensive coordinators in the NFL in Ben Johnson, but to think he is going to continue with that role forever is not realistic. That being said, he does seem very happy in his current position, and if the Lions pay him handsomely, maybe he will stick around for a couple more seasons… or more!