Another funny thing is that the combined userbase of the PS3 and 360 turned out to be almost exactly what was predicted here, it was just a much, much closer race than they thought, but more or less it was still 170m+ between the two.
But Nintendo just made them all look like total dipshits with how the Wii turned out. xD
The chart is a prediction for sell through to 2012, at that point the combined PS360 sales were under 150mln, and the prediction is for 180mln, not terrible but still an overestimate
They lowballed the total of all three by around 45-50mln (combined sales they have at 200mln, when it was more like 245mln)
Given the date of the prediction though it's understandable... this was made before we knew much about the Wii & the whole blue-ocean strategy, Wii flipped things as it took the casual & occasional gamers (which had previously been PS2 owners) as well as selling to new gamers, with hindsight this looks like a bad prediction, but in March 2006 I don't know if I would have made much of a different one.
Counterpoint though is I don't get paid to predict, these kind of firms do.