I can only think of 3 reasons why Meyer wouldn't start.
1. He gets hurt. (this is the only realistic reason in the 3)
2. He proves on gameday he just isn't cut out for it (we've seen him for 3 years already, so something bad will have to happen)
3. in Practice, he isn't pushing himself to get better and earn his job. (I'd say, knowing how he came in and took the job from Flynn, that this would be next to impossible. I just don't see him losing his competetive nature.)
I'd be absolutely baffled as to why Meyer wouldn't start. Not to mention, if someone else does take his job, they better be winning all the games. As I believe he'll have to work for his job, his experience on the field is worth more than just about anything else that could come into play.