I don't think it's a good comparison, the chart is about software not hardware sales. It should be of no surprise an 8yr old console that already built up a large library, install base, and still being supported is going to sell more software.
I think software sales don't drop as fast as hardware sales during a gen transition. I'm pretty sure both PS360 will have higher software sales than PS4 and XB1 for months after thier launch.