So yeah, that happened rather covertly.
Only confirmation so far is a reddit thread(!) with Grace_CA stating this-
On Steam, it should automatically refund you for your pre-order and you have to pre-order again at the new price, as far as I'm aware.
So the question is why. Most likely is they simply aren't making enough pre-orders following the outcry over Chaos DLC, and the hefty price tag of £50 (A major factor in me not pre-ordering).
Thoughts?