Sony is worldwide sales king and there is no reasons it won't win again in 2019 if there is a permanent price cut down to 200 for the slim and 250 for the pro or maybe 300 more realisticly. Ghost of tsushima, last of us 2, death stranding, days gone etc will maintain interest in it as well
No 2019 is definitely a Switch win. At this point in a systems life (6th year) price cuts dont lead to YoY growth, they just help the decline from not being as large. Also, Switch has the potential to receive its own price cut or revision anyway and has big games as well like Fire Emblem, Luigi's Mansion, Animal Crossing & Pokemon Gen 8.
I'm guessing PS4 will see a 10-20% YoY drop and NSW will see a 10-20% YoY gain.
When the herd loses its way, the shepard must kill the bull that leads them astray.