Slope > 0: The rolling hit rate is trending up. The brain is getting better as it sees more data. Good.
Slope ≈ 0: Plateaued. Either you hit your ceiling, or the model needs a refresh / new features.
Slope < 0: Degrading. Possible regime change. Investigate drift, consider retraining or pausing.

Most edge accumulates slowly. A 1%/month improvement in hit rate compounds enormously over a year. Don't expect step changes.