Ethereum is defined by a spec, rather than a reference client. There are seven independent implementations so far. So it's already a less centralized development model.

Once the transition is made to proof-of-stake, the incentives of its "miners" will be more closely aligned to those of the community.

The existing miners can't prevent that transition. They're also using general-purpose hardware that can be repointed to other chains or sold to gamers, so they don't have a strong incentive to fight it anyway.