It's sold close to 3m in the past and this one has more publicity, a holiday release, and is launch title (see Resistance and Motostorm last gen to see how that helps). It think if Resistance can do 4m being a launch title KZ can do 6m. I'll go with that. Not astronomical but it'll launch the series into Uncharted territory for this one at least (I think it'll be awhile before they come back to Killzone)