Like discussed in this thread, these abilities need to be before the attack is declared (declaring an attack is the same as declaring target), otherwise the abilities would not do their job. You can only declare targets you can attack, so any change in how to define targets as valid need to happen before declaring target.
How Trick Shot, Target Acquired, Combat Spotter, Marksman, and Priority Target interact with the figures moving during attack depends on their wording and how the target is moving (or other figures are). It will be harder to get out of line of sight when figures are ignored in the attack (Priority Target, Combat Spotter, Target Acquired, Marksman) while determining line of sight. The target needs to move around a corner or blocking space or blocking terrain edge.
Trick Shot chooses one space to draw line of sight from. If the target moves, it needs to escape line of sight from that space.
