Found this rumor over at reddit, it's still not confirmed, some are saying GS employees don't have a clue about it whilst some others are saying they've gotten confirmation from GS managers.

Either way, the deal should be you trade in your PS3 copy and you get half the price for it so you'd end up paying $25 for it, and the offer should run from July 27 - August 2nd.

Let's check back on the 27th, and hope it's true.