We are now into a new phase of mining, and corporations are taking control of the space and offering the retail investor an opportunity to get in on the action in the form of leases (cloudhashing, hashpower, etc.).
Anyone can mine, and a lot of people do that.
It is not centralized at all ...
In the future, difficulty will decrease, and it should be easy to maintain the network.
Miners will only get some fees to pay for electricity.