QUESTION

When declaring an attack using Hypersonic Speed on a opposing fig. who has Shape Change , does the attacker have to commit to the move prior to the shape change dice roll ?

While I don’t have the rules with me (I am at work...)

You would still have to commit to the move like so:

Hyper-Attacker: Takes POWER: moves x speed to attack figure SC. SC uses shape change.

If the shape change succeeds your attacker must select someone else that they can legally target from their current square. If they cannot target someone they may still move their remaining squares.

Otherwise the action continues as normal. Hope that helps!

The confusion is because the correct order isn't being followed.

Running Shot:
Declare and give figure a power action.
Move figure up to half its speed value.
Choose your target
<here is where Shape-Change would occur>


RCE:
Declare and give figure a power action.
Decide how the modification will be used (+2 to attack, +2 to damage, or +1 to each)
Choose your target
<here is where Shape-Change would occur>


HSS:
Declare and give figure a power action.
Move up to the figure's full movement.
End movement 1.
Declare your target
<here is where Shape-Change would occur>

Hope that helps.