There is no centralization that will happen with Ethereum's POS. Everybody can participate in the staking for as long as they have the minimum number of ETH requirement. Unlike Ethereum shifting to POS, POW coins are somehow under the influence of giant miners that are holding so much power. And unlike POW coins, POS coins does not consume much of the earth's energy and contribute to the the warming climate.
At some point, Ethereum will have some level of centralization with the adoption of PoS. It'll be much more decentralized than its competitors (like EOS and TRON), but much more centralized than PoW coins like Bitcoin and Litecoin. The number of ETH required for staking could result to be extremely expensive in the long run, as prices rise across the crypto market. Still though, anyone with enough money could get into participating in ETH's consensus unlike EOS. In EOS, there's vote buying where Block Producers offer users a share of their reward in exchange for votes. There's also the issue of Block Producers voting for themselves, which is a real issue for those who're whales (effectively increasing the risk of centralization).
While PoW may be energy intensive, it's more decentralized than PoS or DPoS. It also strengthens the security of the Blockchain by a greater degree than the previously mentioned consensus algorithms. It's no wonder why Bitcoin is still the world's most secure cryptocurrency to date, despite being dominated by big players in the mining industry. Even so, PoW has some level of centralization which could put the underlying Blockchain network at risk. This tell us, that there's no consensus algorithm that's perfect in maintaining 100% decentralization.
Nonetheless, PoS may lead to ETH's centralization but not at the degree of other blockchains like EOS and TRON. EOS can only support 21 Block Producers at a time, while ETH has no limit. This means that ETH will become more decentralized in the long run, as more validators join the network. As long as the 32 ETH requirement is met, anyone can secure the ETH blockchain without restrictions. In EOS, you'd need to be highly prominent and widely recognizable within the crypto industry to get a chance to be accepted as a Block Producer. If you manage to get the required number of votes to start producing blocks, then you'll be able to participate in EOS' consensus. Otherwise, you'll be out of the game. That's why, I believe that ETH's PoS will be far more decentralized than DPoS used by EOS, TRON, Tezos, and others. Just my thoughts
