I think Gears of War is a good barometer for MGS4. I suspect MGS will end (not counting if it gets bundled later in life) with 4-5m in sales and be pretty close to the first GeoW. It will do very well (unless the game completely sucks ass) and will boost hardware a decent amount for the PS3, though it will never touch the massive numbers of the original MGS, or even MGS2 for that matter.
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