The problem is that we don't even know the exact PS2 shipments. By Sony PR
, we have 150m as of January 31 2011, and they have shipped 3.8 million from January 1 2011 to September 30 2011. We need to know how many of the 1.2 million shipped from January 1 to March 31 that were shipped during January and thus included in the 150m PR. Assuming even shipments of 400k in all three months gives us an LTD of 153.4 million, but I'm not sure it's an assumption you can make.
Meanwhile, DS is at 149 million and Nintendo expects to ship 3.42 million systems from October to March compared to 1.4 million PS2s that Sony expects to ship in the same period. I'm hoping that if the 3DS really gets going this holiday, Nintendo will be confident enough in it to grant the DS it's budget period ($99 DSi) so that the aforementioned uncertainty becomes irrelevant.