[onestone]

Yes, a soft fork means consensus (majority) among miners. The developers (of Geth, Parity, cpp-ethereum, etc.) can propose the changes, but it's up to the miners whether to adopt them.

Note that the Ethereum mining community is considerably more decentralized than e.g. Bitcoin.

[mikeyouse]

Unless I'm reading this incorrectly, two mining pools control over 50% of the hash rate:

https://etherchain.org/statistics/miners

2/3 of the hashrate from three pools doesn't seem very decentralized.