I think traditionally the assistant head coach is considered, at least, a very strong favorite as a potential new HC if the old coach retires or takes another position. Scott had reason to think he was that guy, and I think it was implied that he would be the next guy. On the other hand OSU has a right to do whatever they think is necessary and John Smith retiring opened up a tremendous opportunity to land David Taylor. Taylor has done a great job and I don't think there's any doubt OSU is a lot better than they'd have been if Smith had hung around or if they'd hired Scott. They got several elite transfers they'd have never gotten otherwise.
Still, I think Scott will probably get a HC job somewhere else. He's already shown how good he was before.