OK, let's all try and be reasonable!
PS3: If we're talking minimums, I can see this system theoretically selling an average of 100K/week worldwide for the next 5 years. Obviously higher on holidays, but this is also taking into account the "last year" slump (assuming *roughly* a 6-year life), that would be 26 million, on top of the 3.42 they've already got. Since my estimations went to the conservative, I'll give a bump and say the minimum would be 35 million.
Wii: Wow, this is the hardest to predict a *minimum* for. Geez, we haven't even seen any sales trends that weren't directly affected by supply yet. I don't think it'll sell as well as the DS (a family may buy 2 or 3 handhelds, but probably will only buy one console), but I definitely see it doing better than PSP. So somewhere in-between. Those two have been out for almost a combined 5 years, and combining their current numbers, you get 66 million. I don't see Wii being cut before the 6 year mark, but my little calculation didn't take into account the fact that DS and PSP haven't had their last-year slump yet. let's call this the minimum: 60 million
X360: I've said it somewhere before, but we're going to find out in September if Microsoft is really going to expand their market. Honestly, I think there's still a stark possibility that they may grab *only* original X-box adopters, plus a couple million in change. Again, since we're talking minimums, I'll say 30 million