The issue is Microsoft have never shown themselves to be greater marathon runners. They did so well last generation in a sprint mentality. It was since 2011 when it became a marathon they really saw their global lead on PS3 shrink. Sony has that global brand and foot print to be able to sell at tiers giving them long legs.
I will say the US is still very much up for grabs, but it is almost impossible to see the global difference do anything but widen in the coming years.