Wow. GT4's second week was huge. If early estimates hold true and GT5 matches its predescessor's first week then I don't see why it wouldn't be able to match its second week considering it will be December by then.
Let's say...
500k EMEAA
200k America
150k Japan
At least 800k second week, with small drops after week 3. Should be able to do 4-4.5 million








