I don't think they'd necessarily lose power over accounts that didn't.
Given two situations:
- Accounts over 8k earn a proportional percentage of inflation based on account size
- Accounts under 8k earn curation rewards based on performance
It's very likely that you could create a voting algorithm that would outperform the proportional percentage of inflation. So in fact, a smart dev could probably earn more by dividing up their stake into smaller accounts and continue to play the curation game just like they do today.
I'm happy to be wrong here, but until math proves it, I've got to believe that the system that's based on performance (as opposed to flat percentage) will be more profitable.
To be completely honest, the only solution I see to the problem you present is to completely remove curation rewards. Whales would stop voting on content to just earn rewards, and would leave room for the actual members of the community to vote on what they find interesting/valuable.