Key note: Constantinople doesn't really scale Eth that much directly. What it does(aka more time) lead to making sharding(coming 2020) to be made "safe" and plasma chains to be made aka thing of Loom network but with Loom tokens and more "trustless". True Plasma chains will be interesting to see be added, the only other type of sidechain tech that exists is Drivechains. POS wasn't really needed if you look at the tech side but POS would lead to better governance(which will lead to decentralization but more order). POW is a chaos based system where no side has power and as such one simple upgrade took 2 years to add....
POW on a money level is awesome but on a platform level...? It could work platform level but needs a lot of work to be done :P