Although it looks bad for Sony, it still dominates the market. Just because sales of the PS2 declined doesn't mean that it didn't out sell both the Xbox and GCN. And, granted, those two consoles did see a jump in sales but they weren't selling all that well anyway so the jump in sales is a bit overrated.
What I see in all of this, hopefully, is that the gap between the dominant PS2 and the Xbox/GCN is closing. All three are great consoles in their own right and it seems that gamers have room in their hearts for more than one console.