If Microsoft can't be a leader with a one year before it's major competitor and with the number of 3rd party serie stolen from Sony i don't think Microsoft can ever be the leader.
PS4 - over 100 millions let's say 120m
Xbox One - 70m
Wii U - 25m
Vita - 15m if it will not get Final Fantasy Kingdoms Heart and Monster Hunter 20m otherwise
3DS - 80m