For quite some time now, I have been a proponent of PPC as a likely candiate to go to 0.X, or >BTC per unit.
The reason being it is better at BTC than what BTC does. That is a long term store of large value.
I would expect PPC to go to 0.01 fairly soon, another 2 years maybe 0.3, and 5 years about 1:1.
It maybe that in the longer term BTC has to adopt the PPC model.
While one might say that BTC should adopt the PPC model (specifically proof of stake) to reduce its maintenance cost and improve its security, there is no practical way for it to do so. Adopting proof of stake would require Bitcoin miners to relinquish their claim on BTC income and cause them to fail to get ROI and profit on their mining equipment. So the interests of Bitcoin miners are completely at odds with proof of stake, while at the same time only the miners get a vote in protocol changes. BTC will never adopt proof of stake.