Can Bitcoin transition from PoW to PoS?

What does it mean for a cryptocurrency to "transition from PoW to PoS"? What does it mean for decentralized entities to come to a consensus on a massive change to how they operate?

 Decentralized governance is really hard, and chains split all the time - remember Bitcoin Classic? Ethereum Classic? All pretty dead now, but in their day they represented substantial chain splits that took a long time to fully resolve.

So, I would say that such a transition is mostly a question of decentralized governance, not a question of technology. If Bitcoin "transitioned to PoS", what actually would have happened is that someone invented a whole new PoS cryptocurrency with very little relationship to Bitcoin, and managed to convince everyone that this new cryptocurrency was actually Bitcoin and that they should all immediately switch. That's really really hard to do!

So, one might wonder why Ethereum seems to be able to do this and yet Bitcoin is a much harder nut to crack. I think the biggest reason is the nature of the decentralized governance of both cryptocurrencies. Bitcoin was effectively released into the wild to fend for itself from Satoshi's initial implementation. Ethereum, on the other hand, has always had a strong steering hand in the Ethereum Foundation. Because there is a concept of legitimate  governance within the Ethereum ecosystem, it's a lot easier to roll out breaking upgrades. But make no mistake - even with this stronger governance, the Ethereum PoW->PoS upgrade is effectively the same as the one described above, where we're swapping out the existing protocol with something pretty different and just trying to convince everyone that its the "legitimate continuation" of that protocol.

The Bitcoin community is largely anti-innovation when it comes to protocol changes. Miners that make billions per year have influence in Bitcoin. It doesn't have the kind of leadership that Ethereum has that can make a decision to transition to PoS. 

It is technically possible. "Materially", Bitcoin is nothing if a record of transactions and the wallet balances it implies. Anybody can come and fork Bitcoin into a new chain which preserves the transactions but changes the implementation and/or the features (as happened with Bitcoin Cash).

The real question is what people believe to be valuable. In this case, what they perceive to be the "real Bitcoin" (currency is a social contract, yadda yadda).

A transition from PoW to PoS must thus find broad community consensus, in particular leadership consensus (but broader consensus is also needed so as to prevent the value of Bitcoin from collapsing).

So who controls the decentralized "uncensorable" currency? Mostly, the miners. The Bitcoin foundation also has power, but as I understand the two are (or at least were) fairly enmeshed.

Of course, miners don't want to transition to PoS, as they would lose their golden goose.

Therefore, it's likely that a transition from PoW would only happen if it is necessary to fend off an existential thread to Bitcoin (which would make mining equally worthless). That could be regulation on PoW, or simply the Ethereum narrative taking over. The point is that the writing has to be on the wall that if Bitcoin doesn't transition, then it is headed to zero, even if it's on a longer timeframe. 

Being much more speculative, I'm going to venture and say that a long-decline of Bitcoin is unlikely. At best, there will be an ambiguous uncertainty period where the Bitcoin faith machine will churn faster than ever, but some proposals for PoS transition will start to emerge and be taken seriously (currently, they're quite unpopular). The ambiguous period will either end with PoS adoption, or with a rapid collapse.

A transition to PoS would probably entail a long phase-out of mining, probably by means of decreased rewards so that established players can amortize their hardware investments.

It's also possible that a PoS bitcoin fork is created (just like Bitcoin Cash) and ends up overtaking the original as the "real Bitcoin" in people's mind. I wouldn't be surprised if such a fork already exists, but timing & support is crucial. A 8-year old forks in 5 years is not going to cut it — it needs to arrive on the scene with as much publicity as possible.

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From the perspective of a store of value, I’m starting to think the costs are a feature, not a bug. Bitcoin is the most popular>huge fees to transact>more miners for bitcoin>bitcoin is more popular. Requiring more energy in some way means firms that mine have higher costs, there was an according use of resources on one side of the ledger from the value of the bitcoin it created. In 101 talk, it’s worth what people will buy it for, but I can’t help but think that those costs to mine find their way into the prices somehow—not just energy, but entrepreneurship and fixed costs. That is to say, congestion begets high price for mining, which begets higher prices in bitcoin, which is the main idea for like 99% of bitcoin users