Does a matter-wave that is destined to decohere become physical before the decoherence event?

Decay of Coherence is something that can happen to decoherent particles. Coherent matter-waves do not decay.

The reason decoherence can be predestined is because unobserved quantum waves do not have restrictions on future decoherence events. Waves are not physical, they are not using Spacetime. The quantum field has a separate timeline (temporal regulator) than the one used for Spacetime. We know they have a time rate from the limit set on light/causality. The quantum field using its own time explains the diffraction trajectory a physical particle has.

A wave does the journey, stretching the entire distance. If decoherence is experienced, the wave condenses to be a wave packet back at the beginning (this might be an entanglement type event - like two waves going through two slits of the double slit experiment).

There may be a third step. After the particle becomes a condensed wave packet back at the beginning, the particle jumps to catch up to the distance the wave would have made without the decoherence event. This jump might look like a condensed wave packet at the beginning of the full wave length, it would shrink but build up at the advanced end like a tunneling wave. After the tunnel, the wave is now physical, using spacetime, and can now decay.

We know it does this back-n-forth because the delayed choice quantum eraser demonstrates a particle of a pair landing on its final panel first, knowing if it’s entangled brother will decohere in its path.