Yes, you can delay the appearance of the augmentation, for example you could define something like a "detectionTime" private variable in your class and set it in the OnTrackingFound; then, in the Update() method, you could compute elapsed time since the detectionTime and enable the renderer components when the elapsed time is large enough.

You can also think of similar but slightly different strategies; all in all, this is simple application logic and about C# programming.