Max: 10.5mil
Min: 8mil
I can't see the Min/Max being too far apart from each other next year - unless Sony really starts hurting financially, the HD consoles' sales should stay reasonably close. For reference, even with the momentum swings this year, the min/max was 5.5mil / 8mil for 2008.
I also think the 360 will have a better year overall (hence, the 8mil minimum). The scenario I imagine is the 360 continuing to pull away during most of the year, until FFXIII / GT5 / price cut in the second half of they ear helps the PS3 catch up. I see the gap being around 9mil or so at the end of 09.
Actually, I've little confidence in this prediction (shot in the dark pretty much), but whatever...