@powergirlfan:You might be right (I have no idea), but I don't believe they intended to give her back her iconic costume from the beginning. From what I gather, Kevin Maguire took a lot of flak for his costume change and wanted to appease Power Girl's fans as much as possible by having the "boob window" appear regularly either through costume destruction or civilian clothing.
I think what we are seeing here is DC finally giving the fans what they wanted in an effort to boost sales on Worlds' Finest. And I know that at least in my case it will work. I had no interest in ever picking up an issue of WF. (I actually haven't touched the New 52 at all.) But with PG being the first character with any semblance of her prior self back, I will start giving the book a try with #12.