Well this gen over 6-8 years so far Wii:100m, PS360: ~80m each (IIRC)
So 260 million this gen.
Of course it looks like Wii U will come nowhere near Wii. Personally I think that means PS4/1 will pick up at least much of the slack and sell more, but some seem think they'll meander along to 70m each like this gen.
MS can talk all they want about 1 billion units, I dont think they have a prayer at 499. The key to that is going to be low pricing. And starting at a high point means it's that much harder/longer to get to the low price points.
I remember seeing MS estimates in the 300-350 range and I think those estimate were over 10 years or life of the next gen consoles. This gen has a chance to hit 300 if it carries on for a few more years.