We all know the theory: Bitcoin and cryptocurrencies are good because they are decentralized, and so on, blah blah blah.
However, as times goes by Bitcoin & C. seem to be less and less decentralized, ...
There is no need to panic. Cryptocurrencies may not be as decentralized as you had hoped, but they can still succeed.
... as big whales become ever bigger while they manage to swallow rising percentages of the coins' supplies, ...
A person holding 1 million BTC has no more control over Bitcoin than a person holding 1 BTC, except for the fact that they could potentially kill it (and lose all of their money in the process).
... and as the serious mining is concentrating in lesser and lesser hands, those few who can afford gigantic mining farms with cheap energy cost. ...
Anyone with access to cheap electricity can mine profitably regardless of the size of their operation. Having a large operation does help because of economies of scale, but it is not clear that there is a problem.
Furthermore, the largest miners are
mining pools, and they are not a threat to decentralization. Mining pools may consist of hundreds or thousands of participants who can join or leave at will. We have seen in the past that when a mining pool becomes a problem, the participants will leave and the pool will disappear.
... We all can see how the cryptocurrency markets can be manipulated by whales (with their infamous Pump & Dumps) ...
The manipulation of markets by whales is a myth. Nobody has ever produced any evidence of this occurring in any meaningful way. It's a great story, but so far it is fiction and not fact.
Furthermore, pump-and-dumps are not done by whales (it would be far too risky). That belief is a myth perpetuated by a lack of understanding of how a pump-and-dump works. Pump-and-dumps are done by scammers running "pump groups". Who needs a whale when you have a thousands of victims following your "signals"?
Regardless, manipulation of markets has no effect on decentralization, except that manipulation could be used to kill a coin.
...
And now the news has arrived of countries willing to do their own cryptocurrencies. Venezuela has just launched the Petro, Iran is planning its coin and apparently so does Russia - and I'd bet many more countries will soon follow. These currencies are all likely to be centralized.
Moreover, banks will probably launch their own centralized cryptocurrencies, and so will corporations. The future looks like a place with more and more centralized cryptocurrencies in competition and less and less truly decentralized cryptocurrencies, as Bitcoin & C. end up in the hands of lesser and lesser people - the super-whales. Which will be the implications of all this?
I think this is a real issue. A currency depends on the network effect to maintain its utility. If people choose centralized currencies over decentralized currencies, then the decentralized currencies will struggle to survive.