Actually I think it's not necessarily going to be announced at E3. The ad shows a limited time offer, it's the most straightforward to read it as a price cut that follows after the sales period if any. Sony can test the water by watching the demand for $499 PS3 at certain retailers then decide.
In a more conspiracy-oriented scenario, it can be a pressure on Sony put by a certain retailer to force a price cut for sales boost and not at all arranged by Sony, or just a fire sale.
In a more conspiracy-oriented scenario, it can be a pressure on Sony put by a certain retailer to force a price cut for sales boost and not at all arranged by Sony, or just a fire sale.