Cannot see it having a big impact.
Once the intial OPC Corsa die-hards have taken up their quota I would think they will trickle out the door.
All reviews have been positive and maybe with VW`s DSG issues it may sway some to pass on the Polo Gti ( VW Sales have dropped 20% since the recall )
I reckon give Opel a few years to settle in, pretty crowded marketplace !